Environ Microbiol
February 2017
Environmental heat stress impacts on the physiology and viability of microbial cells with concomitant implications for microbial activity and diversity. Previously, it has been demonstrated that gradual heating of Saccharomyces cerevisiae induces a degree of thermal resistance, whereas a heat shock results in a high level of cell death. Here, we show that the impact of exogenous nutrients on acquisition of thermal resistance differs between strains.
View Article and Find Full Text PDFThe deltaproteobacterium Myxococcus xanthus predates upon members of the soil microbial community by secreting digestive factors and lysing prey cells. Like other Gram-negative bacteria, M. xanthus produces outer membrane vesicles (OMVs), and we show here that M.
View Article and Find Full Text PDFAlthough typically cosseted in the laboratory with constant temperatures and plentiful nutrients, microbes are frequently exposed to much more stressful conditions in their natural environments where survival and competitive fitness depend upon both growth rate when conditions are favourable and on persistence in a viable and recoverable state when they are not. In order to determine the role of genetic heterogeneity in environmental fitness we present a novel approach that combines the power of fluorescence-activated cell sorting with barcode microarray analysis and apply this to determining the importance of every gene in the Saccharomyces cerevisiae genome in a high-throughput, genome-wide fitness screen. We have grown > 6000 heterozygous mutants together and exposed them to a starvation stress before using fluorescence-activated cell sorting to identify and isolate those individual cells that have not survived the stress applied.
View Article and Find Full Text PDFAppl Environ Microbiol
August 2011
Determination of microbial viability by the plate count method is routine in microbiology laboratories worldwide. However, limitations of the technique, particularly with respect to environmental microorganisms, are widely recognized. Many alternatives based upon viability staining have been proposed, and these are often combined with techniques such as image analysis and flow cytometry.
View Article and Find Full Text PDFAdv Biochem Eng Biotechnol
May 2014
Flow cytometry is an important technique in cell biology and immunology and has been applied by many groups to the analysis of microorganisms. This has been made possible by developments in hardware that is now sensitive enough to be used routinely for analysis of microbes. However, in contrast to advances in the technology that underpin flow cytometry, there has not been concomitant progress in the software tools required to analyse, display and disseminate the data and manual analysis, of individual samples remains a limiting aspect of the technology.
View Article and Find Full Text PDFFor microorganisms in particular, viability is a term that is difficult to define and a state consequently difficult to measure. The traditional (and gold-standard) usage equates viability and culturability (i.e.
View Article and Find Full Text PDFUsing competition experiments in continuous cultures grown in different nutrient environments (glucose limited, ammonium limited, phosphate limited and white grape juice), we identified genes that show haploinsufficiency phenotypes (reduced growth rate when hemizygous) or haploproficiency phenotypes (increased growth rate when hemizygous). Haploproficient genes (815, 1,194, 733 and 654 in glucose-limited, ammonium-limited, phosphate-limited and white grape juice environments, respectively) frequently show that phenotype in a specific environmental context. For instance, genes encoding components of the ubiquitination pathway or the proteasome show haploproficiency in nitrogen-limited conditions where protein conservation may be beneficial.
View Article and Find Full Text PDFThe detection of mycoplasma in milk can be performed by either culture techniques or polymerase chain reaction (PCR) based methods. Although PCR can reduce the average diagnostic time to 5 h in comparison with the several days for the isolation of the agent, there is still a need to develop methods, which could give earlier results. For this purpose, we tested the ability of flow cytometry (FC) to detect mycoplasmas in milk samples.
View Article and Find Full Text PDFIn this study, flow cytometry was evaluated for the determination of the minimal inhibitory concentrations (MIC) of seven antibacterial agents (enrofloxacin, ciprofloxacin, gentamicin, streptomycin, chloramphenicol, oxytetracycline, and tylosin) on Mycoplasma (M.) agalactiae. Flow cytometry was able to detect M.
View Article and Find Full Text PDFFlow cytometry together with SYBR green I and propidium iodide was used to study the effects of enrofloxacin, ciprofloxacin, gentamicin, chloramphenicol, oxytetracycline, and tylosin on four mycoplasma species. Inhibition of mycoplasma growth could be detected by as early as 3 h after the start of treatment. The strongest effect was observed with enrofloxacin- and ciprofloxacin-treated cells.
View Article and Find Full Text PDFOne element of classical systems analysis treats a system as a black or grey box, the inner structure and behaviour of which can be analysed and modelled by varying an internal or external condition, probing it from outside and studying the effect of the variation on the external observables. The result is an understanding of the inner make-up and workings of the system. The equivalent of this in biology is to observe what a cell or system excretes under controlled conditions - the 'metabolic footprint' or exometabolome - as this is readily and accurately measurable.
View Article and Find Full Text PDFAppl Environ Microbiol
October 2004
Diploid cells of Saccharomyces cerevisiae were grown under controlled conditions with a Bioscreen instrument, which permitted the essentially continuous registration of their growth via optical density measurements. Some cultures were exposed to concentrations of a number of antifungal substances with different targets or modes of action (sterol biosynthesis, respiratory chain, amino acid synthesis, and the uncoupler). Culture supernatants were taken and analyzed for their "metabolic footprints" by using direct-injection mass spectrometry.
View Article and Find Full Text PDFA directed evolutionary approach is described that searches short, random peptide sequences for appendage at the secretory signal peptide-mature protein junction to seek ideal algorithms for both efficient and hyper export of recombinant proteins to the periplasm of Escherichia coli. The strategy employs simple, visual detection of positive clones using a PINK expression system that faithfully reports on export status of a mammalian hemoprotein in E. coli.
View Article and Find Full Text PDFFlow cytometry (FCM) is a technique, which allows one to analyse cells rapidly and individually, and permits the quantitative analysis of distributions of a property or properties in a population. It therefore offers many advantages over conventional measurements for the analysis of biological cells. Historically the technique has been widely applied for the study of mammalian cells, but its use in microbiology has been more limited; this is mainly a consequence of the smaller size of microbes, which results in the smaller optical signals that can be obtained from them.
View Article and Find Full Text PDFMany technologies have been developed to help explain the function of genes discovered by systematic genome sequencing. At present, transcriptome and proteome studies dominate large-scale functional analysis strategies. Yet the metabolome, because it is 'downstream', should show greater effects of genetic or physiological changes and thus should be much closer to the phenotype of the organism.
View Article and Find Full Text PDFFlow cytometry is a powerful technique for the study of single cells, and thus it is of particular utility in the study of heterogeneity in microbial populations. This review seeks to highlight the role of flow cytometric analyses in studies of microbial heterogeneity, drawing wherever possible on recently published research articles. Whilst microbial heterogeneity is well documented in both natural and laboratory environments, the underlying causes are less well understood.
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