Two general strategies exist for the growth and survival of prokaryotes in environments of elevated osmolarity. The 'salt in cytoplasm' approach, which requires extensive structural modifications, is restricted mainly to members of the Halobacteriaceae. All other species have convergently evolved to cope with environments of elevated osmolarity by the accumulation of a restricted range of low molecular mass molecules, termed compatible solutes owing to their compatibility with cellular processes at high internal concentrations. Herein we review the molecular mechanisms governing the accumulation of these compounds, both in Gram-positive and Gram-negative bacteria, focusing specifically on the regulation of their transport/synthesis systems and the ability of these systems to sense and respond to changes in the osmolarity of the extracellular environment. Finally, we examine the current knowledge on the role of these osmostress responsive systems in contributing to the virulence potential of a number of pathogenic bacteria. ß

Listeria monocytogenes must resist the deleterious actions of bile in order to infect and subsequently colonize the human gastrointestinal tract. The molecular mechanisms used by the bacterium to resist bile and the influence of bile on pathogenesis are as yet largely unexplored. This study describes the analysis of three genes-bsh, pva, and btlB-previously annotated as bile-associated loci in the sequenced L. monocytogenes EGDe genome (lmo2067, lmo0446, and lmo0754, respectively). Analysis of deletion mutants revealed a role for all three genes in resisting the acute toxicity of bile and bile salts, particularly glycoconjugated bile salts at low pH. Mutants were unaffected in the other stress responses examined (acid, salt, and detergents). Bile hydrolysis assays demonstrate that L. monocytogenes possesses only one bile salt hydrolase gene, namely, bsh. Transcriptional analyses and activity assays revealed that, although it is regulated by both PrfA and B , the latter appears to play the greater role in modulating bsh expression. In addition to being incapable of bile hydrolysis, a sigB mutant was shown to be exquisitely sensitive to bile salts. Furthermore, increased expression of sigB was detected under anaerobic conditions and during murine infection. A gene previously annotated as a possible penicillin V amidase (pva) or bile salt hydrolase was shown to be required for resistance to penicillin V but not penicillin G but did not demonstrate a role in bile hydrolysis. Finally, animal (murine) studies revealed an important role for both bsh and btlB in the intestinal persistence of L. monocytogenes.

Since the completion of the Human Genome project at the turn of the Century, there has been an unprecedented proliferation of genomic sequence data. A consequence of this is that the medical discoveries of the future will largely depend on our ability to process and analyse large genomic data sets, which continue to expand as the cost of sequencing decreases. Herein, we provide an overview of cloud computing and big data technologies, and discuss how such expertise can be used to deal with biology's big data sets. In particular, big data technologies such as the Apache Hadoop project, which provides distributed and parallelised data processing and analysis of petabyte (PB) scale data sets will be discussed, together with an overview of the current usage of Hadoop within the bioinformatics community.

High-pressure processing (HPP) is a nonthermal process capable of inactivating and eliminating pathogenic and food spoilage microorganisms. This novel technology has enormous potential in the food industry, controlling food spoilage, improving food safety and extending product shelf life while retaining the characteristics of fresh, preservative-free, minimally processed foods. As with other food processing methods, such as thermal processing, HPP has somewhat limited applications as it cannot be universally applied to all food types, such as some dairy and animal products and shelf-stable low-acid foods. Herein, we discuss the effects of high-pressure processing on microbial food safety and, to a lesser degree, food quality.

The success of Listeria monocytogenes as a food-borne pathogen owes much to its ability to survive a variety of stresses, both in the external environment prior to ingestion and subsequently within the animal host. Growth at high salt concentrations and low temperatures is attributed mainly to the accumulation of organic solutes such as glycine betaine and carnitine. We utilized a novel system for generating chromosomal mutations (based on a lactococcal pWVO1-derived Ori ؉ RepA ؊ vector, pORI19) to identify a listerial OpuC homologue. Mutating the operon in two strains of L. monocytogenes revealed significant strain variation in the observed activity of OpuC. Radiolabeled osmolyte uptake studies, together with growth experiments in defined media, linked OpuC to carnitine and glycine betaine uptake in Listeria. We also investigated the role of OpuC in contributing to the growth and survival of Listeria in an animal (murine) model of infection. Altering OpuC resulted in a significant reduction in the ability of Listeria to colonize the upper small intestine and cause subsequent systemic infection following peroral inoculation.Survival of the food-borne pathogen Listeria monocytogenes, both at high salt concentrations (29) and in low-temperature environments (45), is attributed mainly to the accumulation of the organic compounds glycine betaine (N,N,N-trimethylglycine [21,32]) and carnitine (␤-hydroxy-␥-N-trimethyl aminobutyrate [5]).The preferred compatible solute for the majority of bacteria (9, 10) and the most important osmolyte in L. monocytogenes is the trimethylammonium compound glycine betaine (4). Present at relatively high concentrations in foods of plant origin (14), it has been shown to stimulate the growth of L. monocytogenes between 0.3 to 0.7 M NaCl (2) and at temperatures as low as 4°C (21). Recent studies identified genes encoding two glycine betaine transport systems in Listeria. The first of these, betL (37, 39), encodes a single-component membrane-bound protein belonging to a family of secondary transporters of which OpuD of Bacillus subtilis (18) and BetP of Corynebacterium glutamicum (34) are members. Transporters in this family couple ion motive force to solute transport across the cell membrane (36). The second system, encoded by the gbuABC operon (22), is a multicomponent, binding protein-dependent transport system, forming part of a superfamily of prokaryotic and eukaryotic ATP-binding cassette transporters (15). Members of this family, including OpuA (20) and OpuC (ProU) (25) of B. subtilis, couple ATP hydrolysis to substrate translocation across biological membranes.After glycine betaine, L-carnitine is regarded as the most effective osmolyte in L. monocytogenes (21,43). Playing a role in fatty acid transport across the inner mitochondrial membrane (17), carnitine can be accumulated to concentrations of up to 50 mM in some animal tissues (6), approximately 5,000-fold more than the previously calculated K m value (10 M) for Listeria (42). However, carnitine is not as effective as glycine ...