qPCR in Food Microbiology

from Luca Cocolin and Kalliopi Rantsiou writing in Quantitative Real-time PCR in Applied Microbiology:

Since its first application in food microbiology in the late '90s, quantitative PCR (qPCR) has attracted the interest of researchers, working mainly in the field of food safety, but lately also of microbiologists studying spoilage and fermentation processes. In addition to the advantages that conventional PCR offers in microbiological testing, i.e. specificity, reduced time of analysis and detection of viable but not culturable cells, qPCR allows quantification of target populations. This aspect is particularly relevant for foodborne pathogens, for which specific microbiological criteria exist, but also for spoilage and technological important microorganisms, in order to follow their population kinetics in foods. Although advancements in food microbiology have been made from its application, qPCR has not yet been utilized to its full potential: the quantification step is only rarely carried out and qPCR is often used as an alternative of conventional PCR. In this chapter authors will critically describe the application of qPCR in food microbiology based on the available literature, taking into account the specific problems and suggesting some possible solutions.

Indication for Co-evolution of Lactobacillus johnsonii with its hosts

The intestinal microbiota, composed of complex bacterial populations, is host-specific and affected by environmental factors as well as host genetics. One important bacterial group is the lactic acid bacteria (LAB), which include many health-promoting strains. This study show the genetic variation within a potentially probiotic LAB species, Lactobacillus johnsonii, isolated from various hosts.

A wide survey of 104 fecal samples was carried out for the isolation of L. johnsonii. As part of the isolation procedure, terminal restriction fragment length polymorphism (tRFLP) was performed to identify L. johnsonii within a selected narrow spectrum of fecal LAB. The tRFLP results showed host specificity of two bacterial species, the Enterococcus faecium species cluster and Lactobacillus intestinalis, to different host taxonomic groups while the appearance of L. johnsonii and E. faecalis was not correlated with any taxonomic group. The survey ultimately resulted in the isolation of L. johnsonii from few host species The genetic variation among the 47 L. johnsonii strains isolated from the various hosts was analyzed based on variation at simple sequence repeats (SSR) loci and multi-locus sequence typing (MLST) of conserved hypothetical genes. The genetic relationships among the strains inferred by each of the methods were similar, revealing three different clusters of L. johnsonii strains, each cluster consisting of strains from a different host, i.e., chickens, humans or mice.

Results support phylogenetic separation of L. johnsonii strains isolated from different animal hosts, suggesting specificity of L. johnsonii strains to their hosts. Taken together with the tRFLP results, that indicated the association of specific LAB species with the host taxonomy, the study supports co-evolution of the host and its intestinal lactic acid bacteria.

Original Source:

Predicting Disease Transmission from Geo-Tagged Micro-Blog Data

Researchers have begun to mine social network data in order to predict a variety of social, economic, and health related phenomena. While previous work has focused on predict- ing aggregate properties, such as the prevalence of seasonal influenza in a given country, researchers consider the task of fine- grained prediction of the health of specific people from noisy and incomplete data.

Quorum sensing in the probiotic bacterium Escherichia coli Nissle 1917 (Mutaflor) - evidence that furanosyl borate diester (AI-2) is influencing the cytokine expression in the DSS colitis mouse model

"Quorum sensing" (QS) is the phenomenon which allows single bacterial cells to measure the concentration of bacterial signal molecules. Two principle different QS systems are known, the Autoinducer 1 system (AI-1) for the intraspecies communication using different Acyl-homoserine lactones (AHL) and AI-2 for the interspecies communication.

Folate status of gut microbiome affects Caenorhabditis elegans lifespan

In a paper in BMC Biology Virk et al. show that Caenorhabditis elegans lifespan is extended in response to a diet of folate-deficient Escherichia coli.
The deficiencies in folate biosynthesis were due to an aroD mutation, or treatment of E. coli with sulfa drugs, which are mimics of the folate precursor para-aminobenzoic acid. This study suggests that pharmacological manipulation of the gut microbiome folate status may be a viable approach to slow animal aging, and raises questions about folate supplementation.

Original Source:

Microbiology Pills: Prokaryotes versus Eukaryotes

Antisense RNA that affects Rhodopseudomonas palustris quorum-sensingsignal receptor expression

Quorum sensing in the bacterium Rhodopseudomonas palustris involves the RpaI signal synthase, which produces p-coumaroyl-homoserine lactone (pC-HSL) and RpaR, which is a pC-HSL–dependent transcriptional activator. There is also an antisense rpaR transcript (asrpaR) of unknown function. Recent RNAseq studies have revealed that bacterial antisense RNAs are abundant, but little is known about the function of these molecules.