The relationship between desiccation and the production of extracellular polysaccharides (EPS) by soil bacteria was investigated by using a Pseudomonas species isolated from soil. Cultures subjected to desiccation while growing in a sand matrix contained more EPS and less protein than those growing at high water potential, suggesting that resources were allocated to EPS production in response to desiccation. Desiccation did not have a significant effect on activity as measured by reduction of iodonitrotetrazolium. Purified EPS produced by the Pseudomonas culture contained several times its weight in water at low water potential. Sand amended with EPS held significantly more water and dried significantly more slowly than unamended sand, implying that an EPS matrix may buffer bacterial colonies from some effects of desiccation. We conclude that bacteria may use EPS production to alter their microenvironment to enhance survival of desiccation.

The Practical Handbook of Microbiology

Relationship between Desiccation and Exopolysaccharide Production in a Soil Pseudomonas sp

Soil organic matter (SOM) consists of a vast range of biomolecules, but their individual contribution to the biogeochemical cycling of nutrients and CO2 release has eluded researchers. Here, we review the current knowledge on combining biomarker with stable isotope analyses for identifying the mechanisms and rates of SOM genesis and transformation. After an overview of the major biomarkers that are used for identifying decomposer communities and the origin of SOM far beyond microbial life cycles, we reexplain the principles and potentials of applying artificial and natural stable isotope labeling techniques in soil research. Major focus is finally laid on the quantitative evaluation of the published compound-specific stable isotope data of soils to characterize the niches and activity of soil microorganisms as well as their role in controlling the short-to long-term fate of SOM. Our literature research suggested that fungi appear to feed mainly on fresh plant material, whereas gram-positive bacteria also consume both fresh and older SOM. The newly synthesized structures have apparent mean residence time (MRT) of 1–80 years, while refractory plant-derived biomarkers may even dissipate faster. In no case did we find evidences for inert soil C. However, MRT was not constant but increased with increasing time after C3/C4 vegetation change. It is concluded that calculated MRTs from C3/C4 vegetation changes are currently underestimated, because,there is also a the formation of stable C4-derived C pools that did not reach steady-state equilibrium within few decades.

Combining biomarker with stable isotope analyses for assessing the transformation and turnover of soil organic matter

One of the major advances in medical science has been the development of antimicrobials; however, a consequence of their widespread use has been the emergence of drug-resistant populations of microorganisms. There is clearly a need for the development of new antimicrobials – but more importantly, there is the need for the development of new classes of antimicrobials, rather than drugs based upon analogues of known scaffolds. Due to the success of the platinum anticancer agents, there has been considerable interest in the development of therapeutic agents based upon other transition metals – and in particular ruthenium(II/III) complexes, due to their well known interaction with DNA. There have been many studies of the anticancer properties and cellular localisation of a range of ruthenium complexes in eukaryotic cells over the last decade. However, only very recently has there been significant interest in their antimicrobial properties. This review highlights the types of ruthenium complexes that have exhibited significant antimicrobial activity and discusses the relationship between chemical structure and biological processing – including site(s) of intracellular accumulation – of the ruthenium complexes in both bacterial and eukaryotic cells.

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Ruthenium complexes as antimicrobial agents.

Atmospheric cold plasma (ACP) is a promising nonthermal technology effective against a wide range of pathogenic microorganisms. Reactive oxygen species (ROS) play a crucial inactivation role when air or other oxygen-containing gases are used. With strong oxidative stress, cells can be damaged by lipid peroxidation, enzyme inactivation, and DNA cleavage. Identification of ROS and an understanding of their role are important for advancing ACP applications for a range of complex microbiological issues. In this study, the inactivation efficacy of in-package high-voltage (80 kV [root mean square]) ACP (HVACP) and the role of intracellular ROS were investigated. Two mechanisms of inactivation were observed in which reactive species were found to either react primarily with the cell envelope or damage intracellular components. Escherichia coli was inactivated mainly by cell leakage and low-level DNA damage. Conversely, Staphylococcus aureus was mainly inactivated by intracellular damage, with significantly higher levels of intracellular ROS observed and little envelope damage. However, for both bacteria studied, increasing treatment time had a positive effect on the intracellular ROS levels generated.

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Mechanisms of Inactivation by High-Voltage Atmospheric Cold Plasma Differ for Escherichia coli and Staphylococcus aureus

The yeasts constitute a large and heterogeneous group of microorganisms that are currently attracting increased attention from scientists and industry. Numerous and diverse biological activities make them promising candidates for a wide range of applications not limited to the food sector. In addition to their major contribution to flavor development in fermented foods, their antagonistic activities toward undesirable bacteria and fungi are now widely known. These activities are associated with their competitiveness for nutrients, acidification of their growth medium, their tolerance of high concentrations of ethanol, and release of antimicrobial compounds such as antifungal killer toxins or “mycocins” and antibacterial compounds. While the design of foods containing probiotics (microorganisms that confer health benefits) has focused primarily on Lactobacillus and Bifidobacterium, the yeast Saccharomyces cerevisiae var. boulardii has long been known effective for treating gastroenteritis. In this review, the antimicrobial activities of yeasts are examined. Mechanisms underlying this antagonistic activity as well as recent applications of these biologically active yeasts in both the medical and veterinary sectors are described.

/pdf/antimicrobial-and-probiotic-properties-of-yeasts-from-4yoao5nrcf.pdf

The Practical Handbook of Microbiology

Citations

Relationship between Desiccation and Exopolysaccharide Production in a Soil Pseudomonas sp

Combining biomarker with stable isotope analyses for assessing the transformation and turnover of soil organic matter

Ruthenium complexes as antimicrobial agents.

Mechanisms of Inactivation by High-Voltage Atmospheric Cold Plasma Differ for Escherichia coli and Staphylococcus aureus

Antimicrobial and Probiotic Properties of Yeasts: From Fundamental to Novel Applications