Characterization of the Highly Autolytic Lactococcus lactis subsp. cremoris Strains CO and 2250

Abstract

Two highly autolytic Lactococcus lactis subsp. cremoris strains (CO and 2250) were selected and analyzed for their autolytic properties. Both strains showed maximum lysis when grown in M17 broth containing a limiting concentration of glucose (0.4 to 0.5%) as the carbohydrate source. Lysis did not vary greatly with pH or temperature but was reduced when strains were grown on lactose or galactose. Growth in M17 containing excess glucose (1%) prevented autolysis, although rapid lysis of L. lactis subsp. cremoris CO did occur in the presence of 1% glucose if sodium fluoride (an inhibitor of glycolysis) was added to the medium. Maximum cell lysis in a buffer system was observed early in the stationary phase, and for CO, two pH optima were observed for log-phase and stationary-phase cells (6.5 and 8.5, respectively). Autolysins were extracted from the cell wall fraction of each strain by using either 4% sodium dodecyl sulfate (SDS), 6 M guanidine hydrochloride, or 4 M lithium chloride, and their activities were analyzed by renaturing SDS-polyacrylamide gel electrophoresis on gels containing Micrococcus luteus or L. lactis subsp. cremoris CO cells as the substrate. More than one lytic band was observed on each substrate, with the major band having an apparent molecular mass of 48 kDa for CO. Each lytic band was present throughout growth and lysis. These results suggest that at least two different autolytic enzymes are present in the autolytic L. lactis subsp. cremoris strains. The presence of the lactococcal cell wall hydrolase gene,

Optimisation of production and storage stability of the starter bacteria Streptococcus thermophilus and Lactobacillus plantarum

“…Autolysis has been previously reported for S. thermophilus at the end of the growth phase in M17 medium containing a limited lactose concentration (5 g L −1 ), as well as lysis prevention at high lactose concentration (>15 g L −1 ) 20–24. Other authors state that autolysis of microbial cells is induced near neutral pH, and the optimal pH for autolysis is generally between pH 6.0 and 7.0 25–27. That autolysis was not produced here, was due either to the cultures being non‐autolytic, or the low pH values in the fermented M17 media being unfavourable to autolysis.…”

Role of Temperate Bacteriophage ϕ20617 on Streptococcus thermophilus DSM 20617T Autolysis and Biology

“…Moreover, the use of the glycolytic inhibitor sodium oxamate and its triggering of autolysis allowed us to link this phenotype to the decreased of cell energetic level (Figures 2A , 3 ). The involvement of the energetic metabolism in cell autolysis was previously observed in L. lactis ( Riepe et al, 1997 ), in Enterococcus faecalis ( Shockman et al, 1961 ) and in B. subtilis ( Joliffe and Streips, 1981 ), but it was never related to a lytic cycle of a temperate prophage.…”

Comparison of Immunogenicity and Protection of Two Pneumococcal Protein Vaccines Based on PsaA and PspA

“…Bacteriumlike particles (BLPs), once called Gram-positive enhancer matrix (GEM), are based on nongenetically modified Gram-positive bacteria and can be used to potentially enhance mucosal vaccines. They consist of nonliving bacterium-shaped delivery particles with adjuvant properties, which can easily be loaded with antigens containing a cell wall binding domain, called protein anchor (PA) (16). The BLPs are made from acidpretreated Lactococcus lactis bacteria, with their original size and structures of about 1 m retained, and are thus ideally sized for uptake by the M cells on the mucosal surface.…”