Next Issue
Previous Issue

Table of Contents

Microorganisms, Volume 3, Issue 3 (September 2015) , Pages 310-587

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
View options order results:
result details:
Displaying articles 1-16
Export citation of selected articles as:
Open AccessArticle
Membrane Association and Catabolite Repression of the Sulfolobus solfataricus α-Amylase
Microorganisms 2015, 3(3), 567-587; https://doi.org/10.3390/microorganisms3030567
Received: 17 June 2015 / Revised: 10 August 2015 / Accepted: 11 September 2015 / Published: 18 September 2015
Cited by 1 | Viewed by 2271 | PDF Full-text (1012 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Sulfolobus solfataricus is a thermoacidophilic member of the archaea whose envelope consists of an ether-linked lipid monolayer surrounded by a protein S-layer. Protein translocation across this envelope must accommodate a steep proton gradient that is subject to temperature extremes. To better understand this [...] Read more.
Sulfolobus solfataricus is a thermoacidophilic member of the archaea whose envelope consists of an ether-linked lipid monolayer surrounded by a protein S-layer. Protein translocation across this envelope must accommodate a steep proton gradient that is subject to temperature extremes. To better understand this process in vivo, studies were conducted on the S. solfataricus glycosyl hydrolyase family 57 α-Amylase (AmyA). Cell lines harboring site specific modifications of the amyA promoter and AmyA structural domains were created by gene replacement using markerless exchange and characterized by Western blot, enzyme assay and culture-based analysis. Fusion of amyA to the malAp promoter overcame amyAp-mediated regulatory responses to media composition including glucose and amino acid repression implicating action act at the level of transcription. Deletion of the AmyA Class II N-terminal signal peptide blocked protein secretion and intracellular protein accumulation. Deletion analysis of a conserved bipartite C-terminal motif consisting of a hydrophobic region followed by several charged residues indicated the charged residues played an essential role in membrane-association but not protein secretion. Mutants lacking the C-terminal bipartite motif exhibited reduced growth rates on starch as the sole carbon and energy source; therefore, association of AmyA with the membrane improves carbohydrate utilization. Widespread occurrence of this motif in other secreted proteins of S. solfataricus and of related Crenarchaeota suggests protein association with membranes is a general trait used by these organisms to influence external processes. Full article
(This article belongs to the Special Issue Extremophiles)
Figures

Figure 1

Open AccessArticle
Evaluation of Potential Effects of NaCl and Sorbic Acid on Staphylococcal Enterotoxin A Formation
Microorganisms 2015, 3(3), 551-566; https://doi.org/10.3390/microorganisms3030551
Received: 18 June 2015 / Revised: 3 August 2015 / Accepted: 1 September 2015 / Published: 17 September 2015
Cited by 4 | Viewed by 1852 | PDF Full-text (931 KB) | HTML Full-text | XML Full-text
Abstract
The prophage-encoded staphylococcal enterotoxin A (SEA) is recognized as the main cause of staphylococcal food poisoning (SFP), a common foodborne intoxication disease, caused by Staphylococcus aureus. Studies on the production of SEA suggest that activation of the SOS response and subsequent prophage [...] Read more.
The prophage-encoded staphylococcal enterotoxin A (SEA) is recognized as the main cause of staphylococcal food poisoning (SFP), a common foodborne intoxication disease, caused by Staphylococcus aureus. Studies on the production of SEA suggest that activation of the SOS response and subsequent prophage induction affect the regulation of the sea gene and the SEA produced, increasing the risk for SFP. The present study aims to evaluate the effect of NaCl and sorbic acid, in concentrations relevant to food production, on SOS response activation, prophage induction and SEA production. The impact of stress was initially evaluated on steady state cells for a homogenous cell response. NaCl 2% was found to activate the SOS response, i.e., recA expression, and trigger prophage induction, in a similar way as the phage-inducer mitomycin C. In contrast, sorbic acid decreased the pH of the culture to a level where prophage induction was probably suppressed, even when combined with NaCl stress. The impact of previous physiological state of the bacteria was also addressed on cells pre-exposed to NaCl, and was found to potentially affect cell response upon exposure to further stress. The results obtained highlight the possible SFP-related risks arising from the use of preservatives during food processing. Full article
(This article belongs to the Special Issue Microbial Activity in Food)
Figures

Figure 1

Open AccessArticle
Effect of Lemongrass Essential Oil Vapors on Microbial Dynamics and Listeria monocytogenes Survival on Rocket and Melon Stored under Different Packaging Conditions and Temperatures
Microorganisms 2015, 3(3), 535-550; https://doi.org/10.3390/microorganisms3030535
Received: 27 July 2015 / Accepted: 1 September 2015 / Published: 9 September 2015
Cited by 2 | Viewed by 1822 | PDF Full-text (742 KB) | HTML Full-text | XML Full-text
Abstract
The aim of the present study was to examine the effect of lemongrass essential oil vapors on the dynamics of surface microbiota and L. monocytogenes growth on rocket and melon under different packaging conditions and storage temperature. For that purpose, rocket and [...] Read more.
The aim of the present study was to examine the effect of lemongrass essential oil vapors on the dynamics of surface microbiota and L. monocytogenes growth on rocket and melon under different packaging conditions and storage temperature. For that purpose, rocket and melon were placed on Expanded Polystyrene (EPS) trays, sprayed with L. monocytogenes to a population of 4.5–5.0 log CFU·g−1, packaged using microperforated Oriented Polypropylene (OPP) film in either air or Microperforated Active Modified Atmosphere (MAMA) (initial atmosphere 5% O2, 10% CO2) including a Whatman paper containing the essential oil, without contact with the product, and stored at 0, 5, 10, and 15 °C. Application of lemongrass exhibited a bactericidal effect on enterococci and a fungistatic effect on yeast-mould populations but only during air storage of rocket. The former took place at all temperatures and the latter only at 10 and 15 °C. No effect on shelf life of both products was recorded. However, an important effect on the sensorial properties was observed; during the first 4–5 days of storage both products were organoleptically unacceptable. Regarding MAMA packaging, it affected only Pseudomonas spp. population resulting in a reduction of 1–2 log CFU·g−1 in both products. Full article
(This article belongs to the Special Issue Microbial Activity in Food)
Open AccessArticle
The Effects of Perchlorates on the Permafrost Methanogens: Implication for Autotrophic Life on Mars
Microorganisms 2015, 3(3), 518-534; https://doi.org/10.3390/microorganisms3030518
Received: 30 June 2015 / Revised: 30 July 2015 / Accepted: 1 September 2015 / Published: 9 September 2015
Cited by 6 | Viewed by 2026 | PDF Full-text (761 KB) | HTML Full-text | XML Full-text
Abstract
The terrestrial permafrost represents a range of possible cryogenic extraterrestrial ecosystems on Earth-like planets without obvious surface ice, such as Mars. The autotrophic and chemolithotrophic psychrotolerant methanogens are more likely than aerobes to function as a model for life forms that may exist [...] Read more.
The terrestrial permafrost represents a range of possible cryogenic extraterrestrial ecosystems on Earth-like planets without obvious surface ice, such as Mars. The autotrophic and chemolithotrophic psychrotolerant methanogens are more likely than aerobes to function as a model for life forms that may exist in frozen subsurface environments on Mars, which has no free oxygen, inaccessible organic matter, and extremely low amounts of unfrozen water. Our research on the genesis of methane, its content and distribution in permafrost horizons of different ages and origin demonstrated the presence of methane in permanently frozen fine-grained sediments. Earlier, we isolated and described four strains of methanogenic archaea of Methanobacterium and Methanosarcina genera from samples of Pliocene and Holocene permafrost from Eastern Siberia. In this paper we study the effect of sodium and magnesium perchlorates on growth of permafrost and nonpermafrost methanogens, and present evidence that permafrost hydogenotrophic methanogens are more resistant to the chaotropic agent found in Martian soil. In this paper we study the effect of sodium and magnesium perchlorates on the growth of permafrost and nonpermafrost methanogens, and present evidence that permafrost hydogenotrophic methanogens are more resistant to the chaotropic agent found in Martian soil. Furthermore, as shown in the studies strain M2T M. arcticum, probably can use perchlorate anion as an electron acceptor in anaerobic methane oxidation. Earth’s subzero subsurface environments are the best approximation of environments on Mars, which is most likely to harbor methanogens; thus, a biochemical understanding of these pathways is expected to provide a basis for designing experiments to detect autotrophic methane-producing life forms on Mars. Full article
(This article belongs to the Special Issue Extremophiles)
Figures

Figure 1

Open AccessArticle
A Three-Component Microbial Consortium from Deep-Sea Salt-Saturated Anoxic Lake Thetis Links Anaerobic Glycine Betaine Degradation with Methanogenesis
Microorganisms 2015, 3(3), 500-517; https://doi.org/10.3390/microorganisms3030500
Received: 1 July 2015 / Revised: 27 July 2015 / Accepted: 1 September 2015 / Published: 9 September 2015
Cited by 4 | Viewed by 2140 | PDF Full-text (1018 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Microbial communities inhabiting the deep-sea salt-saturated anoxic lakes of the Eastern Mediterranean operate under harsh physical-chemical conditions that are incompatible with the lifestyle of common marine microorganisms. Here, we investigated a stable three-component microbial consortium obtained from the brine of the recently discovered [...] Read more.
Microbial communities inhabiting the deep-sea salt-saturated anoxic lakes of the Eastern Mediterranean operate under harsh physical-chemical conditions that are incompatible with the lifestyle of common marine microorganisms. Here, we investigated a stable three-component microbial consortium obtained from the brine of the recently discovered deep-sea salt-saturated Lake Thetis. The trophic network of this consortium, established at salinities up to 240, relies on fermentative decomposition of common osmoprotectant glycine betaine (GB). Similarly to known extreme halophilic anaerobic GB-degrading enrichments, the initial step of GB degradation starts with its reductive cleavage to trimethylamine and acetate, carried out by the fermenting member of the Thetis enrichment, Halobacteroides lacunaris TB21. In contrast to acetate, which cannot be easily oxidized in salt-saturated anoxic environments, trimethylamine represents an advantageous C1-substrate for methylotrophic methanogenic member of the Thetis enrichment, Methanohalophilus sp. TA21. This second member of the consortium likely produces hydrogen via methylotrophic modification of reductive acetyl-CoA pathway because the initial anaerobic GB cleavage reaction requires the consumption of reducing equivalents. Ecophysiological role of the third member of the Thetis consortium, Halanaerobium sp. TB24, which lacks the capability of either GB or trimethylamine degradation, remains yet to be elucidated. As it is true for cultivated members of family Halanaerobiaceae, the isolate TB24 can obtain energy primarily by fermenting simple sugars and producing hydrogen as one of the end products. Hence, by consuming of TB21 and TA21 metabolites, Halanaerobium sp. TB24 can be an additional provider of reducing equivalents required for reductive degradation of GB. Description of the Thetis GB-degrading consortium indicated that anaerobic degradation of osmoregulatory molecules may play important role in the overall turnover of organic carbon in anoxic hypersaline biotopes. Full article
(This article belongs to the Special Issue Extremophiles)
Figures

Figure 1

Open AccessArticle
Novel Methanotrophs of the Family Methylococcaceae from Different Geographical Regions and Habitats
Microorganisms 2015, 3(3), 484-499; https://doi.org/10.3390/microorganisms3030484
Received: 10 July 2015 / Revised: 4 August 2015 / Accepted: 7 August 2015 / Published: 21 August 2015
Cited by 12 | Viewed by 2866 | PDF Full-text (664 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Terrestrial methane seeps and rice paddy fields are important ecosystems in the methane cycle. Methanotrophic bacteria in these ecosystems play a key role in reducing methane emission into the atmosphere. Here, we describe three novel methanotrophs, designated BRS-K6, GFS-K6 and AK-K6, which were [...] Read more.
Terrestrial methane seeps and rice paddy fields are important ecosystems in the methane cycle. Methanotrophic bacteria in these ecosystems play a key role in reducing methane emission into the atmosphere. Here, we describe three novel methanotrophs, designated BRS-K6, GFS-K6 and AK-K6, which were recovered from three different habitats in contrasting geographic regions and ecosystems: waterlogged rice-field soil and methane seep pond sediments from Bangladesh; and warm spring sediments from Armenia. All isolates had a temperature range for growth of 8–35 °C (optimal 25–28 °C) and a pH range of 5.0–7.5 (optimal 6.4–7.0). 16S rRNA gene sequences showed that they were new gammaproteobacterial methanotrophs, which form a separate clade in the family Methylococcaceae. They fell into a cluster with thermotolerant and mesophilic growth tendency, comprising the genera Methylocaldum-Methylococcus-Methyloparacoccus-Methylogaea. So far, growth below 15 °C of methanotrophs from this cluster has not been reported. The strains possessed type I intracytoplasmic membranes. The genes pmoA, mxaF, cbbL, nifH were detected, but no mmoX gene was found. Each strain probably represents a novel species either belonging to the same novel genus or each may even represent separate genera. These isolates extend our knowledge of methanotrophic Gammaproteobacteria and their physiology and adaptation to different ecosystems. Full article
Figures

Figure 1

Open AccessReview
Role of Bacterial Exopolysaccharides as Agents in Counteracting Immune Disorders Induced by Herpes Virus
Microorganisms 2015, 3(3), 464-483; https://doi.org/10.3390/microorganisms3030464
Received: 1 July 2015 / Revised: 24 July 2015 / Accepted: 5 August 2015 / Published: 21 August 2015
Cited by 8 | Viewed by 3389 | PDF Full-text (1485 KB) | HTML Full-text | XML Full-text
Abstract
Extreme marine environments, such as the submarine shallow vents of the Eolian Islands (Italy), offer an almost unexplored source of microorganisms producing unexploited and promising biomolecules for pharmaceutical applications. Thermophilic and thermotolerant bacilli isolated from Eolian vents are able to produce exopolysaccharides (EPSs) [...] Read more.
Extreme marine environments, such as the submarine shallow vents of the Eolian Islands (Italy), offer an almost unexplored source of microorganisms producing unexploited and promising biomolecules for pharmaceutical applications. Thermophilic and thermotolerant bacilli isolated from Eolian vents are able to produce exopolysaccharides (EPSs) with antiviral and immunomodulatory effects against Herpes simplex virus type 2 (HSV-2). HSV-2 is responsible for the most common and continuously increasing viral infections in humans. Due to the appearance of resistance to the available treatments, new biomolecules exhibiting different mechanisms of action could provide novel agents for treating viral infections. The EPSs hinder the HSV-2 replication in human peripheral blood mononuclear cells (PBMC) but not in WISH (Wistar Institute Susan Hayflic) cells line, indicating that cell-mediated immunity was involved in the antiviral activity. High levels of Th1-type cytokines were detected in PBMC treated with all EPSs, while Th2-type cytokines were not induced. These EPSs are water soluble exopolymers able to stimulate the immune response and thus contribute to the antiviral immune defense, acting as immunomodulators. As stimulants of Th1 cell-mediated immunity, they could lead to the development of novel drugs as alternative in the treatment of herpes virus infections, as well as in immunocompromised host. Full article
(This article belongs to the Special Issue Extremophiles)
Figures

Figure 1

Open AccessArticle
Quantitative Characterization of the Growth of Deinococcus geothermalis DSM-11302: Effect of Inoculum Size, Growth Medium and Culture Conditions
Microorganisms 2015, 3(3), 441-463; https://doi.org/10.3390/microorganisms3030441
Received: 9 June 2015 / Revised: 21 July 2015 / Accepted: 28 July 2015 / Published: 20 August 2015
Cited by 1 | Viewed by 2059 | PDF Full-text (1164 KB) | HTML Full-text | XML Full-text
Abstract
Due to their remarkable resistance to extreme conditions, Deinococcaceae strains are of great interest to biotechnological prospects. However, the physiology of the extremophile strain Deinococcus geothermalis has scarcely been studied and is not well understood. The physiological behaviour was then studied in well-controlled [...] Read more.
Due to their remarkable resistance to extreme conditions, Deinococcaceae strains are of great interest to biotechnological prospects. However, the physiology of the extremophile strain Deinococcus geothermalis has scarcely been studied and is not well understood. The physiological behaviour was then studied in well-controlled conditions in flask and bioreactor cultures. The growth of D. geothermalis type strains was compared. Among the strains tested, the strain from the German Collection of Microorganisms (Deutsche Sammlung von Mikroorganismen DSM) DSM-11302 was found to give the highest biomass concentration and growth rate: in a complex medium with glucose, the growth rate reached 0.75 h−1 at 45 °C. Yeast extract concentration in the medium had significant constitutive and catalytic effects. Furthermore, the results showed that the physiological descriptors were not affected by the inoculum preparation steps. A batch culture of D. geothermalis DSM-11302 on defined medium was carried out: cells grew exponentially with a maximal growth rate of 0.28 h−1 and D. geothermalis DSM-11302 biomass reached 1.4 g·L−1 in 20 h. Then, 1.4 gDryCellWeight of biomass (X) was obtained from 5.6 g glucose (Glc) consumed as carbon source, corresponding to a yield of 0.3 CmolX·CmolGlc−1; cell specific oxygen uptake and carbon dioxide production rates reached 216 and 226 mmol.CmolX−1·h−1, respectively, and the respiratory quotient (QR) value varied from 1.1 to 1.7. This is the first time that kinetic parameters and yields are reported for D. geothermalis DSM-11302 grown on a mineral medium in well-controlled batch culture. Full article
(This article belongs to the Special Issue Extremophiles)
Figures

Figure 1

Open AccessArticle
Assessment of the Factors Contributing to the Growth or Spoilage of Meyerozyma guilliermondii in Organic Yogurt: Comparison of Methods for Strain Differentiation
Microorganisms 2015, 3(3), 428-440; https://doi.org/10.3390/microorganisms3030428
Received: 9 July 2015 / Revised: 30 July 2015 / Accepted: 7 August 2015 / Published: 19 August 2015
Cited by 5 | Viewed by 1930 | PDF Full-text (642 KB) | HTML Full-text | XML Full-text
Abstract
In this work we analyze the spoiling potential of Meyerozyma guilliermondii in yogurt. The analysis was based on contaminated samples sent to us by an industrial laboratory over two years. All the plain and fruit yogurt packages were heavily contaminated by yeasts, but [...] Read more.
In this work we analyze the spoiling potential of Meyerozyma guilliermondii in yogurt. The analysis was based on contaminated samples sent to us by an industrial laboratory over two years. All the plain and fruit yogurt packages were heavily contaminated by yeasts, but only the last ones, containing fermentable sugars besides lactose, were spoiled by gas swelling. These strains were unable to grow and ferment lactose (as the type strain); they did grow on lactate plus galactose, fermented glucose and sucrose, and galactose (weakly), but did not compete with lactic acid bacteria for lactose. This enables them to grow in any yogurt, although only those with added jam were spoiled due to the fermentation of the fruit sugars. Fermentation, but not growth, was strongly inhibited at 8 °C. In consequence, in plain yogurt as well as in any yogurt maintained at low temperature, yeast contamination would not be detected by the consumer. The risk could be enhanced because the species has been proposed for biological control of fungal infections in organic agriculture. The combination of the IGS PCR-RFLP (amplification of the intergenic spacer region of rDNA followed by restriction fragment length polymorphism analysis) method and mitochondrial DNA-RFLP makes a good tool to trace and control the contamination by M. guilliermondii. Full article
(This article belongs to the Special Issue Microbial Activity in Food)
Figures

Figure 1

Open AccessReview
Live Yeast and Yeast Cell Wall Supplements Enhance Immune Function and Performance in Food-Producing Livestock: A Review †,
Microorganisms 2015, 3(3), 417-427; https://doi.org/10.3390/microorganisms3030417
Received: 26 May 2015 / Revised: 17 July 2015 / Accepted: 29 July 2015 / Published: 7 August 2015
Cited by 25 | Viewed by 2587 | PDF Full-text (373 KB) | HTML Full-text | XML Full-text
Abstract
More livestock producers are seeking natural alternatives to antibiotics and antimicrobials, and searching for supplements to enhance growth performance, and general animal health and well-being. Some of the compounds currently being utilized and studied are live yeast and yeast-based products derived from the [...] Read more.
More livestock producers are seeking natural alternatives to antibiotics and antimicrobials, and searching for supplements to enhance growth performance, and general animal health and well-being. Some of the compounds currently being utilized and studied are live yeast and yeast-based products derived from the strain Saccharomyces cerevisiae. These products have been reported to have positive effects both directly and indirectly on the immune system and its subsequent biomarkers, thereby mitigating negative effects associated with stress and disease. These yeast-based products have also been reported to simultaneously enhance growth and performance by enhancing dry matter intake (DMI) and average daily gain (ADG) perhaps through the establishment of a healthy gastrointestinal tract. These products may be especially useful in times of potential stress such as during birth, weaning, early lactation, and during the receiving period at the feedlot. Overall, yeast supplements appear to possess the ability to improve animal health and metabolism while decreasing morbidity, thereby enhancing profitability of these animals. Full article
(This article belongs to the Special Issue Microbial Activity in Food)
Open AccessReview
Pyruvate: A key Nutrient in Hypersaline Environments?
Microorganisms 2015, 3(3), 407-416; https://doi.org/10.3390/microorganisms3030407
Received: 26 June 2015 / Revised: 29 July 2015 / Accepted: 31 July 2015 / Published: 7 August 2015
Cited by 6 | Viewed by 1962 | PDF Full-text (665 KB) | HTML Full-text | XML Full-text
Abstract
Some of the most commonly occurring but difficult to isolate halophilic prokaryotes, Archaea as well as Bacteria, require or prefer pyruvate as carbon and energy source. The most efficient media for the enumeration and isolation of heterotrophic prokaryotes from natural environments, from freshwater [...] Read more.
Some of the most commonly occurring but difficult to isolate halophilic prokaryotes, Archaea as well as Bacteria, require or prefer pyruvate as carbon and energy source. The most efficient media for the enumeration and isolation of heterotrophic prokaryotes from natural environments, from freshwater to hypersaline, including the widely used R2A agar medium, contain pyruvate as a key ingredient. Examples of pyruvate-loving halophiles are the square, extremely halophilic archaeon Haloquadratum walsbyi and the halophilic gammaproteobacterium Spiribacter salinus. However, surprisingly little is known about the availability of pyruvate in natural environments and about the way it enters the cell. Some halophilic Archaea (Halorubrum saccharovorum, Haloarcula spp.) partially convert sugars and glycerol to pyruvate and other acids (acetate, lactate) which are excreted to the medium. Pyruvate formation from glycerol was also shown during a bloom of halophilic Archaea in the Dead Sea. However, no pyruvate transporters were yet identified in the genomes of halophilic Archaea, and altogether, our understanding of pyruvate transport in the prokaryote world is very limited. Therefore, the preference for pyruvate by fastidious and often elusive halophiles and the empirically proven enhanced colony recovery on agar media containing pyruvate are still poorly understood. Full article
(This article belongs to the Special Issue Extremophiles)
Open AccessArticle
Cold-Active, Heterotrophic Bacteria from the Highly Oligotrophic Waters of Lake Vanda, Antarctica
Microorganisms 2015, 3(3), 391-406; https://doi.org/10.3390/microorganisms3030391
Received: 12 June 2015 / Revised: 5 July 2015 / Accepted: 9 July 2015 / Published: 24 July 2015
Cited by 2 | Viewed by 2283 | PDF Full-text (1010 KB) | HTML Full-text | XML Full-text
Abstract
The permanently ice-covered lakes of the McMurdo Dry Valleys, Antarctica are distinctive ecosystems that consist strictly of microbial communities. In this study, water samples were collected from Lake Vanda, a stratified Dry Valley lake whose upper waters (from just below the ice cover [...] Read more.
The permanently ice-covered lakes of the McMurdo Dry Valleys, Antarctica are distinctive ecosystems that consist strictly of microbial communities. In this study, water samples were collected from Lake Vanda, a stratified Dry Valley lake whose upper waters (from just below the ice cover to nearly 60 m) are highly oligotrophic, and used to establish enrichment cultures. Six strains of psychrotolerant, heterotrophic bacteria were isolated from lake water samples from a depth of 50 or 55 m. Phylogenetic analyses showed the Lake Vanda strains to be species of Nocardiaceae, Caulobacteraceae, Sphingomonadaceae, and Bradyrhizobiaceae. All Lake Vanda strains grew at temperatures near or below 0 °C, but optimal growth occurred from 18 to 24 °C. Some strains showed significant halotolerance, but no strains required NaCl for growth. The isolates described herein include cold-active species not previously reported from Dry Valley lakes, and their physiological and phylogenetic characterization broadens our understanding of these limnologically unique lakes. Full article
(This article belongs to the Special Issue Extremophiles)
Figures

Figure 1

Open AccessArticle
Extremophiles in Mineral Sulphide Heaps: Some Bacterial Responses to Variable Temperature, Acidity and Solution Composition
Microorganisms 2015, 3(3), 364-390; https://doi.org/10.3390/microorganisms3030364
Received: 4 June 2015 / Revised: 26 June 2015 / Accepted: 29 June 2015 / Published: 9 July 2015
Cited by 6 | Viewed by 2000 | PDF Full-text (1389 KB) | HTML Full-text | XML Full-text
Abstract
In heap bioleaching, acidophilic extremophiles contribute to enhanced metal extraction from mineral sulphides through the oxidation of Fe(II) and/or reduced inorganic sulphur compounds (RISC), such as elemental sulphur or mineral sulphides, or the degradation of organic compounds derived from the ore, biota or [...] Read more.
In heap bioleaching, acidophilic extremophiles contribute to enhanced metal extraction from mineral sulphides through the oxidation of Fe(II) and/or reduced inorganic sulphur compounds (RISC), such as elemental sulphur or mineral sulphides, or the degradation of organic compounds derived from the ore, biota or reagents used during mineral processing. The impacts of variable solution acidity and composition, as well as temperature on the three microbiological functions have been examined for up to four bacterial species found in mineral sulphide heaps. The results indicate that bacteria adapt to sufficiently high metal concentrations (Cu, Ni, Co, Zn, As) to allow them to function in mineral sulphide heaps and, by engaging alternative metabolic pathways, to extend the solution pH range over which growth is sustained. Fluctuating temperatures during start up in sulphide heaps pose the greatest threat to efficient bacterial colonisation. The large masses of ores in bioleaching heaps mean that high temperatures arising from sulphide oxidation are hard to control initially, when the sulphide content of the ore is greatest. During that period, mesophilic and moderately thermophilic bacteria are markedly reduced in both numbers and activity. Full article
(This article belongs to the Special Issue Extremophiles)
Figures

Figure 1

Open AccessArticle
Copahue Geothermal System: A Volcanic Environment with Rich Extreme Prokaryotic Biodiversity
Microorganisms 2015, 3(3), 344-363; https://doi.org/10.3390/microorganisms3030344
Received: 12 April 2015 / Revised: 9 June 2015 / Accepted: 15 June 2015 / Published: 8 July 2015
Cited by 2 | Viewed by 2038 | PDF Full-text (2153 KB) | HTML Full-text | XML Full-text
Abstract
The Copahue geothermal system is a natural extreme environment located at the northern end of the Cordillera de los Andes in Neuquén province in Argentina. The geochemistry and consequently the biodiversity of the area are dominated by the activity of the Copahue volcano. [...] Read more.
The Copahue geothermal system is a natural extreme environment located at the northern end of the Cordillera de los Andes in Neuquén province in Argentina. The geochemistry and consequently the biodiversity of the area are dominated by the activity of the Copahue volcano. The main characteristic of Copahue is the extreme acidity of its aquatic environments; ponds and hot springs of moderate and high temperature as well as Río Agrio. In spite of being an apparently hostile location, the prokaryotic biodiversity detected by molecular ecology techniques as well as cultivation shows a rich and diverse environment dominated by acidophilic, sulphur oxidising bacteria or archaea, depending on the conditions of the particular niche studied. In microbial biofilms, found in the borders of the ponds where thermal activity is less intense, the species found are completely different, with a high presence of cyanobacteria and other photosynthetic species. Our results, collected during more than 10 years of work in Copahue, have enabled us to outline geomicrobiological models for the different environments found in the ponds and Río Agrio. Besides, Copahue seems to be the habitat of novel, not yet characterised autochthonous species, especially in the domain Archaea. Full article
(This article belongs to the Special Issue Extremophiles)
Figures

Figure 1

Open AccessArticle
Tetrachloromethane-Degrading Bacterial Enrichment Cultures and Isolates from a Contaminated Aquifer
Microorganisms 2015, 3(3), 327-343; https://doi.org/10.3390/microorganisms3030327
Received: 29 April 2015 / Revised: 9 June 2015 / Accepted: 18 June 2015 / Published: 2 July 2015
Cited by 5 | Viewed by 2121 | PDF Full-text (606 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The prokaryotic community of a groundwater aquifer exposed to high concentrations of tetrachloromethane (CCl4) for more than three decades was followed by terminal restriction fragment length polymorphism (T-RFLP) during pump-and-treat remediation at the contamination source. Bacterial enrichments and isolates were obtained [...] Read more.
The prokaryotic community of a groundwater aquifer exposed to high concentrations of tetrachloromethane (CCl4) for more than three decades was followed by terminal restriction fragment length polymorphism (T-RFLP) during pump-and-treat remediation at the contamination source. Bacterial enrichments and isolates were obtained under selective anoxic conditions, and degraded 10 mg·L−1 CCl4, with less than 10% transient formation of chloroform. Dichloromethane and chloromethane were not detected. Several tetrachloromethane-degrading strains were isolated from these enrichments, including bacteria from the Klebsiella and Clostridium genera closely related to previously described CCl4 degrading bacteria, and strain TM1, assigned to the genus Pelosinus, for which this property was not yet described. Pelosinus sp. TM1, an oxygen-tolerant, Gram-positive bacterium with strictly anaerobic metabolism, excreted a thermostable metabolite into the culture medium that allowed extracellular CCl4 transformation. As estimated by T-RFLP, phylotypes of CCl4-degrading enrichment cultures represented less than 7%, and archaeal and Pelosinus strains less than 0.5% of the total prokaryotic groundwater community. Full article
(This article belongs to the Special Issue Microbial C1 Metabolism)
Figures

Figure 1

Open AccessArticle
Temporal Study of the Microbial Diversity of the North Arm of Great Salt Lake, Utah, U.S.
Microorganisms 2015, 3(3), 310-326; https://doi.org/10.3390/microorganisms3030310
Received: 14 May 2015 / Revised: 12 June 2015 / Accepted: 15 June 2015 / Published: 2 July 2015
Cited by 9 | Viewed by 2233 | PDF Full-text (1217 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We employed a temporal sampling approach to understand how the microbial diversity may shift in the north arm of Great Salt Lake, Utah, U.S. To determine how variations in seasonal environmental factors affect microbial communities, length heterogeneity PCR fingerprinting was performed using consensus [...] Read more.
We employed a temporal sampling approach to understand how the microbial diversity may shift in the north arm of Great Salt Lake, Utah, U.S. To determine how variations in seasonal environmental factors affect microbial communities, length heterogeneity PCR fingerprinting was performed using consensus primers for the domain Bacteria, and the haloarchaea. The archaeal fingerprints showed similarities during 2003 and 2004, but this diversity changed during the remaining two years of the study, 2005 and 2006. We also performed molecular phylogenetic analysis of the 16S rRNA genes of the whole microbial community to characterize the taxa in the samples. Our results indicated that in the domain, Bacteria, the Salinibacter group dominated the populations in all samplings. However, in the case of Archaea, as noted by LIBSHUFF for phylogenetic relatedness analysis, many of the temporal communities were distinct from each other, and changes in community composition did not track with environmental parameters. Around 20–23 different phylotypes, as revealed by rarefaction, predominated at different periods of the year. Some phylotypes, such as Haloquadradum, were present year-round although they changed in their abundance in different samplings, which may indicate that these species are affected by biotic factors, such as nutrients or viruses, that are independent of seasonal temperature dynamics. Full article
(This article belongs to the Special Issue Extremophiles)
Figures

Figure 1

Microorganisms EISSN 2076-2607 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top