Role of the Sortase A in the Release of Cell-Wall Proteinase PrtS in the Growth Medium of Streptococcus thermophilus 4F44

Growth of the lactic acid bacterium Streptococcus thermophilus in milk depends on its capacity to hydrolyze proteins of this medium through its surface proteolytic activity. Thus, strains exhibiting the cell envelope proteinase (CEP) PrtS are able to grow in milk at high cellular density. Due to its LPNTG motif, which is possibly the substrate of the sortase A (SrtA), PrtS is anchored to the cell wall in most S. thermophilus strains. Conversely, a soluble extracellular PrtS activity has been reported in the strain 4F44. It corresponds, in fact, to a certain proportion of PrtS that is not anchored to the cell wall but rather is released in the growth medium. The main difference between PrtS of strain 4F44 (PrtS4F44) and other PrtS concerns the absence of a 32-residue imperfect duplication in the prodomain of the CEP, postulated as being required for the maturation and correct subsequent anchoring of PrtS. In fact, both mature (without the prodomain at the N-terminal extremity) and immature (with the prodomain) forms are found in the soluble PrtS4F44 form along with an intact LPNTG at their C-terminal extremity. Investigations we present in this work show that (i) the imperfect duplication is not implied in PrtS maturation; (ii) the maturase PrtM is irrelevant in PrtS maturation which is probably automaturated; and (iii) SrtA allows for the PrtS anchoring in S. thermophilus but the SrtA of strain 4F44 (SrtA4F44) displays an altered activity.

Identification of Potential Citrate Metabolism Pathways in Carnobacterium maltaromaticum

In the present study, we describe the identification of potential citrate metabolism pathways for the lactic acid bacterium (LAB) Carnobacterium maltaromaticum. A phenotypic assay indicated that four of six C. maltaromaticum strains showed weak (Cm 6-1 and ATCC 35586) or even delayed (Cm 3-1 and Cm 5-1) citrate utilization activity. The remaining two strains, Cm 4-1 and Cm 1-2 gave negative results. Additional analysis showed no or very limited utilization of citrate in media containing 1% glucose and 22 or 30 mM citrate and inoculated with Cm 6-1 or ATCC 35586. Two potential pathways of citrate metabolism were identified by bioinformatics analyses in C. maltaromaticum including either oxaloacetate (pathway 1) or tricarboxylic compounds such as isocitrate and α-ketoglutarate (pathway 2) as intermediates. Genes encoding pathway 1 were present in two out of six strains while pathway 2 included genes present in all six strains. The two potential citrate metabolism pathways in C. maltaromaticum may potentially affect the sensory profiles of milk and soft cheeses subjected to growth with this species.

Analysis of Transcriptomic Response to SO 2 by Oenococcus oeni Growing in Continuous Culture

Malolactic fermentation is an indispensable step in the elaboration of most wines and is generally performed by Oenococcus oeni , a Gram-positive heterofermentative lactic acid bacterium species. While O. oeni is tolerant to many of the wine stresses, including low pH and high ethanol concentrations, it has high sensitivity to SO 2 , an antiseptic and antioxidant compound regularly used in winemaking.

Three distinct proteases are responsible for overall cell surface proteolysis in Streptococcus thermophilus .

The lactic acid bacterium Streptococcus thermophilus was believed to display only two distinct proteases at the cell surface, namely the cell-envelope protease PrtS and the house-keeping protease HtrA. Using peptidomics, we demonstrate here the existence of an additional active cell-surface protease, which shares significant homology with the SepM protease of Streptococcus mutans . Although all three proteases—PrtS, HtrA, and SepM—are involved in the turnover of surface proteins, they demonstrate distinct substrate specificities. In particular, SepM cleaves proteins involved in cell wall metabolism and cell elongation, and its inactivation has consequences for cell morphology. When all three proteases are inactivated, the residual cell-surface proteolysis of S. thermophilus is approximately 5% of that of the wild-type strain. Importance Streptococcus thermophilus is a lactic acid bacterium widely used as a starter in the dairy industry. Due to its "generally recognized as safe" status and its weak cell-surface proteolytic activity, it is also considered to be a potential bacterial vector for heterologous protein production. Our identification of a new cell surface protease made it possible to construct a mutant strain with a 95% reduction in surface proteolysis, which could be useful in numerous biotechnological applications.

Complete Genome Sequence of Latilactobacillus sp. Strain WDN19, a High- d- Aspartate-Producing Lactic Acid Bacterium Isolated from a Japanese Pickle

We report here the complete genome sequence of Latilactobacillus sp. strain WDN19, isolated from a Japanese pickle. This strain can produce a large amount of d- aspartate in the culture broth. The genome consists of a circular chromosome (1,967,462 bp; GC content, 41.88%) and a circular plasmid (66,648 bp; GC content, 35.08%).

Complete Genome Sequence of Lactobacillus helveticus JCM 1004, an Aminopeptidase-Producing Lactic Acid Bacterium

We report the complete genome sequence of Lactobacillus helveticus JCM 1004, an aminopeptidase-producing lactic acid bacterium. The genome consists of a circular chromosome which comprises 2,261,280 bp, with a G+C content of 37.56%. The genome was predicted to harbor 13 rRNA genes, 64 tRNA genes, and 2,462 protein-coding sequences.