Biodiversity-based identification and functional characterization of the mannose-specific adhesin of Lactobacillus plantarum.

Lactobacillus plantarum is a frequently encountered inhabitant of the human intestinal tract, and some strains are marketed as probiotics. Their ability to adhere to mannose residues is a potentially interesting characteristic with regard to proposed probiotic features such as colonization of the intestinal surface and competitive exclusion of pathogens. In this study, the variable capacity of 14 L. plantarum strains to agglutinate Saccharomyces cerevisiae in a mannose-specific manner was determined and subsequently correlated with an L. plantarum WCFS1-based genome-wide genotype database. This led to the identification of four candidate mannose adhesin-encoding genes. Two genes primarily predicted to code for sortase-dependent cell surface proteins displayed a complete gene-trait match. Their involvement in mannose adhesion was corroborated by the finding that a sortase (srtA) mutant of L. plantarum WCFS1 lost the capacity to agglutinate S. cerevisiae. The postulated role of these two candidate genes was investigated by gene-specific deletion and overexpression in L. plantarum WCFS1. Subsequent evaluation of the mannose adhesion capacity of the resulting mutant strains showed that inactivation of one candidate gene (lp_0373) did not affect mannose adhesion properties. In contrast, deletion of the other gene (lp_1229) resulted in a complete loss of yeast agglutination ability, while its overexpression quantitatively enhanced this phenotype. Therefore, this gene was designated to encode the mannose-specific adhesin (Msa; gene name, msa) of L. plantarum. Domain homology analysis of the predicted 1,000-residue Msa protein identified known carbohydrate-binding domains, further supporting its role as a mannose adhesin that is likely to be involved in the interaction of L. plantarum with its host in the intestinal tract.

Ambiguity of 'snack' in British usage.

Research into least fattening eating patterns indicates that in England 'a snack' is a term that refers to different eating habits from 'snacking' and that neither pattern of behaviour necessarily involves 'snack food'. These hypotheses were tested by randomised mailings to a convenience sample of university campus addressees with the subject heading of the message and the topic of questions in it being one of the terms, a snack, snacking or snack food. Responses to all three terms much more often referred to eating between mealtimes than eating at mealtimes but this contrast was less for a snack, especially at lunchtime. Previous and subsequent eating occasions therefore tended to be at mealtimes, but again less so for a snack. A snack also differed from snacking or eating snack food in eliciting more reports by women of eating in the home than out, and more eating alone than in company. However, reports by men contributed most to differences between snack terms in the foods reported: more men ate bread in a snack than when snacking but more ate sweet items when snacking than in a snack. More men reported savoury items (e.g. potato crisps) as snack food than in response to the other two terms; however, when savouries were combined with bread-containing items, the women were unlike the men in that more of them referred to such items when snacking. Thus, for these people in England, having a snack is not the same thing as snacking or eating snack food. Because of these ambiguities in use of the root word snack, it may be best to avoid all its derivatives in questions to research participants, discussion among investigators and educational messages.