Special Issue "Actinobacteria and Myxobacteria—Important Resources for Novel Antibiotics"

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

Deadline for manuscript submissions: closed (30 April 2018)

Special Issue Editor

Guest Editor
Dr. Joachim Wink

Working Group Microbial Strain Collection, Helmholtz Centre for Infection Research (HZI), Inhoffenstraße 7, D-38124 Braunschweig, Germany
Website | E-Mail
Interests: Polyphasic Taxonomy; Cultivation Methods; Isolation Methods; Taxonomy and secondary metabolites from Actinobacteria and Myxobacteria; Morphology and fine structure of Actinobacteria and Myxobacteria

Special Issue Information

Dear Colleagues,

Bacterial infections cause millions of deaths globally, particularly in children and the elderly, and four of the 10 leading causes of death are infectious diseases in low- and middle-income countries. The continuous use of antibiotics has resulted in multi-resistant bacterial strains all over the world, such as Community-associated Methicillin-resistant Staphylococcus aureus (MRSA), extended-spectrum β-lactamases (ESBLs), and, as expected, hospitals have become breeding grounds for human-associated microorganisms, especially in critical care units.

Natural products are the bedrock and a valuable source for drug discovery programs. More than 60% of the drugs that are available on the market are derived from natural sources. Many antibiotics are made chemically via modification of natural products through a process called semi synthesis. Natural product structures have the characteristics of a high chemical diversity, biochemical specificity, and high binding affinities to their specific receptor and also interact with a wide variety of biological targets.

Microorganisms produce a wide range of natural products, which are used as lead components in the drug discovery era. Over 6000 compounds of microbial origin with anti-microbial activities have been isolated. The microbial world represents 90% of all biological diversity and less than 1% has presently been explored (Molinari 2009). Mining microbial diversity is the key to obtaining high compound diversity, because a very large source for new natural products remains unexplored. To date, a few groups of microorganisms have been known to be high and potent producers of natural products: Actinomycetes, Bacillus, cyanobacteria, fungi and myxobacteria.

Dr. Joachim Wink
Guest Editor

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Keywords

  • Polyphasic Taxonomy
  • Secondary Metabolites
  • Biotechnology
  • Differentiation
  • Biosynthesis
  • Morphology
  • PKS and NRPS

Published Papers (4 papers)

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Research

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Open AccessArticle Evaluation of Antimicrobial, Enzyme Inhibitory, Antioxidant and Cytotoxic Activities of Partially Purified Volatile Metabolites of Marine Streptomyces sp.S2A
Microorganisms 2018, 6(3), 72; https://doi.org/10.3390/microorganisms6030072
Received: 30 April 2018 / Revised: 6 July 2018 / Accepted: 13 July 2018 / Published: 18 July 2018
Cited by 2 | PDF Full-text (11501 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In the present study, marine actinobacteria Streptomyces sp.S2A was isolated from the Gulf of Mannar, India. Identification was carried out by 16S rRNA analysis. Bioactive metabolites were extracted by solvent extraction method. The metabolites were assayed for antagonistic activity against bacterial and fungal [...] Read more.
In the present study, marine actinobacteria Streptomyces sp.S2A was isolated from the Gulf of Mannar, India. Identification was carried out by 16S rRNA analysis. Bioactive metabolites were extracted by solvent extraction method. The metabolites were assayed for antagonistic activity against bacterial and fungal pathogens, inhibition of α-glucosidase and α-amylase enzymes, antioxidant activity and cytotoxic activity against various cell lines. The actinobacterial extract showed significant antagonistic activity against four gram-positive and two gram-negative pathogens. Excellent reduction in the growth of fungal pathogens was also observed. The minimum inhibitory concentration of the partially purified extract (PPE) was determined as 31.25 μg/mL against Klebsiella pneumoniae, 15.62 μg/mL against Staphylococcus epidermidis, Staphylococcus aureus and Bacillus cereus. The lowest MIC was observed against Micrococcus luteus as 7.8 μg/mL. MIC against fungal pathogens was determined as 62.5 μg/mL against Bipolaris maydis and 15.62 μg/mL against Fusarium moniliforme. The α-glucosidase and α-amylase inhibitory potential of the fractions were carried out by microtiter plate method. IC50 value of active fraction for α-glucosidase and α-amylase inhibition was found to be 21.17 μg/mL and 20.46 μg/mL respectively. The antioxidant activity of partially purified extract (PPE) (DPPH, ABTS, FRAP and Metal chelating activity) were observed and were also found to have significant cytotoxic activity against HT-29, MDA and U-87MG cell lines. The compound analysis was performed using gas chromatography-mass spectrometry (GC-MS) and resulted in three constituents; pyrrolo[1–a]pyrazine-1,4-dione,hexahydro-3-(2-methylpropyl)-, being the main component (80%). Overall, the strain possesses a wide spectrum of antimicrobial, enzyme inhibitory, antioxidant and cytotoxic activities which affords the production of significant bioactive metabolites as potential pharmacological agents. Full article
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Review

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Open AccessReview Diversity of Myxobacteria—We Only See the Tip of the Iceberg
Microorganisms 2018, 6(3), 84; https://doi.org/10.3390/microorganisms6030084
Received: 6 June 2018 / Revised: 6 August 2018 / Accepted: 8 August 2018 / Published: 11 August 2018
Cited by 2 | PDF Full-text (6303 KB) | HTML Full-text | XML Full-text
Abstract
The discovery of new antibiotics is mandatory with regard to the increasing number of resistant pathogens. One approach is the search for new antibiotic producers in nature. Among actinomycetes, Bacillus species, and fungi, myxobacteria have been a rich source for bioactive secondary metabolites [...] Read more.
The discovery of new antibiotics is mandatory with regard to the increasing number of resistant pathogens. One approach is the search for new antibiotic producers in nature. Among actinomycetes, Bacillus species, and fungi, myxobacteria have been a rich source for bioactive secondary metabolites for decades. To date, about 600 substances could be described, many of them with antibacterial, antifungal, or cytostatic activity. But, recent cultivation-independent studies on marine, terrestrial, or uncommon habitats unequivocally demonstrate that the number of uncultured myxobacteria is much higher than would be expected from the number of cultivated strains. Although several highly promising myxobacterial taxa have been identified recently, this so-called Great Plate Count Anomaly must be overcome to get broader access to new secondary metabolite producers. In the last years it turned out that especially new species, genera, and families of myxobacteria are promising sources for new bioactive metabolites. Therefore, the cultivation of the hitherto uncultivable ones is our biggest challenge. Full article
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Open AccessReview Antiviral Compounds from Myxobacteria
Microorganisms 2018, 6(3), 73; https://doi.org/10.3390/microorganisms6030073
Received: 25 May 2018 / Revised: 13 July 2018 / Accepted: 17 July 2018 / Published: 19 July 2018
PDF Full-text (1652 KB) | HTML Full-text | XML Full-text
Abstract
Viral infections including human immunodeficiency virus (HIV), cytomegalovirus (CMV), hepatitis B virus (HBV), and hepatitis C virus (HCV) pose an ongoing threat to human health due to the lack of effective therapeutic agents. The re-emergence of old viral diseases such as the recent [...] Read more.
Viral infections including human immunodeficiency virus (HIV), cytomegalovirus (CMV), hepatitis B virus (HBV), and hepatitis C virus (HCV) pose an ongoing threat to human health due to the lack of effective therapeutic agents. The re-emergence of old viral diseases such as the recent Ebola outbreaks in West Africa represents a global public health issue. Drug resistance and toxicity to target cells are the major challenges for the current antiviral agents. Therefore, there is a need for identifying agents with novel modes of action and improved efficacy. Viral-based illnesses are further aggravated by co-infections, such as an HIV patient co-infected with HBV or HCV. The drugs used to treat or manage HIV tend to increase the pathogenesis of HBV and HCV. Hence, novel antiviral drug candidates should ideally have broad-spectrum activity and no negative drug-drug interactions. Myxobacteria are in the focus of this review since they produce numerous structurally and functionally unique bioactive compounds, which have only recently been screened for antiviral effects. This research has already led to some interesting findings, including the discovery of several candidate compounds with broad-spectrum antiviral activity. The present review looks at myxobacteria-derived antiviral secondary metabolites. Full article
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Open AccessReview Chemical Elicitors of Antibiotic Biosynthesis in Actinomycetes
Microorganisms 2018, 6(2), 52; https://doi.org/10.3390/microorganisms6020052
Received: 2 May 2018 / Revised: 4 June 2018 / Accepted: 6 June 2018 / Published: 8 June 2018
Cited by 1 | PDF Full-text (1344 KB) | HTML Full-text | XML Full-text
Abstract
Whole genome sequencing of actinomycetes has uncovered a new immense realm of microbial chemistry and biology. Most biosynthetic gene clusters present in genomes were found to remain “silent” under standard cultivation conditions. Some small molecules—chemical elicitors—can be used to induce the biosynthesis of [...] Read more.
Whole genome sequencing of actinomycetes has uncovered a new immense realm of microbial chemistry and biology. Most biosynthetic gene clusters present in genomes were found to remain “silent” under standard cultivation conditions. Some small molecules—chemical elicitors—can be used to induce the biosynthesis of antibiotics in actinobacteria and to expand the chemical diversity of secondary metabolites. Here, we outline a brief account of the basic principles of the search for regulators of this type and their application. Full article
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