Halophilic Microorganisms, 2nd Edition

A special issue of Microorganisms (ISSN 2076-2607). This special issue belongs to the section "Environmental Microbiology".

Deadline for manuscript submissions: 30 November 2024 | Viewed by 8199

Special Issue Editor


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Guest Editor
Microbiology and Parasitology, University of Sevilla, Sevilla, Spain
Interests: taxonomy; halophilic microorganism; metagenomic; biodiversity
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Special Issue Information

Dear Colleagues,

This Special Issue is the continuation of our previous special issue "Halophilic Microorganisms"

Halophiles are microorganisms adapted for living at hypersaline environments and other saline products. Most of them belong to the bacteria and archaea domains, and their interest is of special relevance both for their adaptation mechanisms to extreme conditions and for their potential biotechnological applications. In recent years, the isolation and taxonomic characterization of halophiles have allowed us to learn more in detail about their heterogeneity, their metabolic and physiological diversity, or ecological distribution and biodiversity. Culture-independent techniques, such as metagenomics and -omics studies, are particularly providing an incentive these studies on halophiles to continue, as there is still an immense field to explore in this regard.

In this Special Issue of Microorganisms, you are invited to send contributions (original articles as well as reviews) concerning the biology, taxonomy, biodiversity, and biotechnological applications of halophilic microorganisms, as well as using genomic and metagenomic approaches to study microbial communities. Information that will improve our understanding of the role of halophilic microorganisms in hypersaline environments, their adaptation to the environmental conditions, their genetic and functional diversity, and their phylogenetic position is especially welcome.

Dr. Cristina Sánchez-Porro
Guest Editor

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Keywords

  • obligate halophiles
  • bacteria
  • archaea
  • taxonomy and biodiversity
  • biotechnology
  • genomics
  • metagenomics
  • physiology and metabolism
  • hypersaline habitats

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Published Papers (5 papers)

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Research

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23 pages, 9333 KiB  
Article
Unique Features of Extremely Halophilic Microbiota Inhabiting Solar Saltworks Fields of Vietnam
by Violetta La Cono, Gina La Spada, Francesco Smedile, Francesca Crisafi, Laura Marturano, Alfonso Modica, Huynh Hoang Nhu Khanh, Pham Duc Thinh, Cao Thi Thuy Hang, Elena A. Selivanova, Ninh Khắc Bản and Michail M. Yakimov
Microorganisms 2024, 12(10), 1975; https://doi.org/10.3390/microorganisms12101975 - 29 Sep 2024
Viewed by 352
Abstract
The artificial solar saltworks fields of Hon Khoi are important industrial and biodiversity resources in southern Vietnam. Most hypersaline environments in this area are characterized by saturated salinity, nearly neutral pH, intense ultraviolet radiation, elevated temperatures and fast desiccation processes. However, the extremely [...] Read more.
The artificial solar saltworks fields of Hon Khoi are important industrial and biodiversity resources in southern Vietnam. Most hypersaline environments in this area are characterized by saturated salinity, nearly neutral pH, intense ultraviolet radiation, elevated temperatures and fast desiccation processes. However, the extremely halophilic prokaryotic communities associated with these stressful environments remain uninvestigated. To fill this gap, a metabarcoding approach was conducted to characterize these communities by comparing them with solar salterns in northern Vietnam as well as with the Italian salterns of Motya and Trapani. Sequencing analyses revealed that the multiple reuses of crystallization ponds apparently create significant perturbations and structural instability in prokaryotic consortia. However, some interesting features were noticed when we examined the diversity of ultra-small prokaryotes belonging to Patescibacteria and DPANN Archaea. Surprisingly, we found at least five deeply branched clades, two from Patescibacteria and three from DPANN Archaea, which seem to be quite specific to the Hon Khoi saltworks field ecosystem and can be considered as a part of biogeographical connotation. Further studies are needed to characterize these uncultivated taxa, to isolate and cultivate them, which will allow us to elucidate their ecological role in these hypersaline habitats and to explore their biotechnological and biomedical potential. Full article
(This article belongs to the Special Issue Halophilic Microorganisms, 2nd Edition)
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20 pages, 2279 KiB  
Article
Halotolerant Endophytic Bacteria Priestia flexa 7BS3110 with Hg2+ Tolerance Isolated from Avicennia germinans in a Caribbean Mangrove from Colombia
by Zamira E. Soto-Varela, Christian J. Orozco-Sánchez, Hernando José Bolívar-Anillo, José M. Martínez, Nuria Rodríguez, Natalia Consuegra-Padilla, Alfredo Robledo-Meza and Ricardo Amils
Microorganisms 2024, 12(9), 1857; https://doi.org/10.3390/microorganisms12091857 - 7 Sep 2024
Viewed by 676
Abstract
The mangrove ecosystems of the Department of Atlántico (Colombian Caribbean) are seriously threatened by problems of hypersalinization and contamination, especially by heavy metals from the Magdalena River. The mangrove plants have developed various mechanisms to adapt to these stressful conditions, as well as [...] Read more.
The mangrove ecosystems of the Department of Atlántico (Colombian Caribbean) are seriously threatened by problems of hypersalinization and contamination, especially by heavy metals from the Magdalena River. The mangrove plants have developed various mechanisms to adapt to these stressful conditions, as well as the associated microbial populations that favor their growth. In the present work, the tolerance and detoxification capacity to heavy metals, especially to mercury, of a halotolerant endophytic bacterium isolated from the species Avicennia germinans located in the Balboa Swamp in the Department of Atlántico was characterized. Diverse microorganisms were isolated from superficially sterilized A. germinans leaves. Tolerance to NaCl was evaluated for each of the obtained isolates, and the most resistant was selected to assess its tolerance to Pb2+, Cu2+, Hg2+, Cr3+, Co2+, Ni2+, Zn2+, and Cd2+, many of which have been detected in high concentrations in the area of study. According to the ANI and AAI percentages, the most halotolerant strain was identified as Priestia flexa, named P. flexa 7BS3110, which was able to tolerate up to 12.5% (w/v) NaCl and presented a minimum inhibitory concentrations (MICs) of 0.25 mM for Hg, 10 mM for Pb, and 15 mM for Cr3+. The annotation of the P. flexa 7BS3110 genome revealed the presence of protein sequences associated with exopolysaccharide (EPS) production, thiol biosynthesis, specific proteins for chrome efflux, non-specific proteins for lead efflux, and processes associated with sulfur and iron homeostasis. Scanning electron microscopy (SEM) analysis showed morphological cellular changes and the transmission electron microscopy (TEM) showed an electrodense extracellular layer when exposed to 0.25 mM Hg2+. Due to the high tolerance of P. flexa 7BS3110 to Hg2+ and NaCl, its ability to grow when exposed to both stressors was tested, and it was able to thrive in the presence of 5% (w/v) NaCl and 0.25 mM of Hg2+. In addition, it was able to remove 98% of Hg2+ from the medium when exposed to a concentration of 14 mg/L of this metalloid. P. flexa 7BS3110 has the potential to bioremediate Hg2+ halophilic contaminated ecosystems. Full article
(This article belongs to the Special Issue Halophilic Microorganisms, 2nd Edition)
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20 pages, 5340 KiB  
Article
The Hypersaline Soils of the Odiel Saltmarshes Natural Area as a Source for Uncovering a New Taxon: Pseudidiomarina terrestris sp. nov
by Cristina Galisteo, Rafael R. de la Haba, Antonio Ventosa and Cristina Sánchez-Porro
Microorganisms 2024, 12(2), 375; https://doi.org/10.3390/microorganisms12020375 - 11 Feb 2024
Cited by 1 | Viewed by 1306
Abstract
The hypersaline soils of the Odiel Saltmarshes Natural Area are an extreme environment with high levels of some heavy metals; however, it is a relevant source of prokaryotic diversity that we aim to explore. In this study, six strains related to the halophilic [...] Read more.
The hypersaline soils of the Odiel Saltmarshes Natural Area are an extreme environment with high levels of some heavy metals; however, it is a relevant source of prokaryotic diversity that we aim to explore. In this study, six strains related to the halophilic genus Pseudidiomarina were isolated from this habitat. The phylogenetic study based on the 16S rRNA gene sequence and the fingerprinting analysis suggested that they constituted a single new species within the genus Pseudidiomarina. Comparative genomic analysis based on the OGRIs indices and the phylogeny inferred from the core genome were performed considering all the members of the family Idiomarinaceae. Additionally, a completed phenotypic characterization, as well as the fatty acid profile, were also carried out. Due to the characteristics of the habitat, genomic functions related to salinity and high heavy metal concentrations were studied, along with the global metabolism of the six isolates. Last, the ecological distribution of the isolates was studied in different hypersaline environments by genome recruitment. To sum up, the six strains constitute a new species within the genus Pseudidiomarina, for which the name Pseudidiomarina terrestris sp. nov. is proposed. The low abundance in all the studied hypersaline habitats indicates that it belongs to the rare biosphere in these habitats. In silico genome functional analysis suggests the presence of heavy metal transporters and pathways for nitrate reduction and nitrogen assimilation in low availability, among other metabolic traits. Full article
(This article belongs to the Special Issue Halophilic Microorganisms, 2nd Edition)
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15 pages, 354 KiB  
Article
Reduction in Salt Stress Due to the Action of Halophilic Bacteria That Promote Plant Growth in Solanum lycopersicum
by Javier Pérez-Inocencio, Gabriel Iturriaga, Cesar L. Aguirre-Mancilla, María Soledad Vásquez-Murrieta, Marcos Alfonso Lastiri-Hernández and Dioselina Álvarez-Bernal
Microorganisms 2023, 11(11), 2625; https://doi.org/10.3390/microorganisms11112625 - 25 Oct 2023
Viewed by 1907
Abstract
Soil salinity is one of the most important factors reducing agricultural productivity worldwide. Halophilic plant growth-promoting bacteria (H-PGPB) represent an alternative method of alleviating saline stress in crops of agricultural interest. In this study, the following halophilic bacteria were evaluated: Bacillus sp. SVHM1.1, [...] Read more.
Soil salinity is one of the most important factors reducing agricultural productivity worldwide. Halophilic plant growth-promoting bacteria (H-PGPB) represent an alternative method of alleviating saline stress in crops of agricultural interest. In this study, the following halophilic bacteria were evaluated: Bacillus sp. SVHM1.1, Halomonas sp. SVCN6, Halomonas sp. SVHM8, and a consortium. They were grown under greenhouse conditions in Solanum lycopersicum at different salinity concentrations in irrigation water (0, 20, 60, and 100 mM NaCl) to determine the effects on germination, fruit quality, yield, and concentration of osmoprotectors in plant tissue. Our results demonstrate the influence of halophilic bacteria with the capacity to promote plant growth on the germination and development of Solanum lycopersicum at higher salinity levels. The germination percentage was improved at the highest concentration by the inoculated treatments (from 37 to 47%), as were the length of the radicle (30% at 20 mM) and plumule of the germinated seed, this bacterium also increased the weight of the plumule (97% at 100 mM). They also improved the yield. The dry weight of the plant, in addition to having an influence on the quality of the fruit and the concentration of osmoprotectors (Bacillus sp. SVHM 1.1) had the greatest effect on fruit yield (1.5 kg/plant at 20 mM), by the otherhand, Halomonas sp. SVHM8 provided the best fruit quality characteristics at 100 mM. According to the above results, the efficiency of halophilic PGPB in the attenuation of salt stress in Solanum lycopersicum has been proven. Full article
(This article belongs to the Special Issue Halophilic Microorganisms, 2nd Edition)
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Review

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20 pages, 694 KiB  
Review
Halophilic Plant-Associated Bacteria with Plant-Growth-Promoting Potential
by McKay Meinzer, Niaz Ahmad and Brent L. Nielsen
Microorganisms 2023, 11(12), 2910; https://doi.org/10.3390/microorganisms11122910 - 2 Dec 2023
Cited by 3 | Viewed by 2552
Abstract
The salinization of soils is a growing agricultural concern worldwide. Irrigation practices, drought, and climate change are leading to elevated salinity levels in many regions, resulting in reduced crop yields. However, there is potential for a solution in the microbiome of halophytes, which [...] Read more.
The salinization of soils is a growing agricultural concern worldwide. Irrigation practices, drought, and climate change are leading to elevated salinity levels in many regions, resulting in reduced crop yields. However, there is potential for a solution in the microbiome of halophytes, which are naturally salt-tolerant plants. These plants harbor a salt-tolerant microbiome in their rhizosphere (around roots) and endosphere (within plant tissue). These bacteria may play a significant role in conferring salt tolerance to the host plants. This leads to the possibility of transferring these beneficial bacteria, known as salt-tolerant plant-growth-promoting bacteria (ST-PGPB), to salt-sensitive plants, enabling them to grow in salt-affected areas to improve crop productivity. In this review, the background of salt-tolerant microbiomes is discussed and their potential use as ST-PGPB inocula is explored. We focus on two Gram-negative bacterial genera, Halomonas and Kushneria, which are commonly found in highly saline environments. These genera have been found to be associated with some halophytes, suggesting their potential for facilitating ST-PGPB activity. The study of salt-tolerant microbiomes and their use as PGPB holds promise for addressing the challenges posed by soil salinity in the context of efforts to improve crop growth in salt-affected areas. Full article
(This article belongs to the Special Issue Halophilic Microorganisms, 2nd Edition)
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