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Effect of exopolysaccharides on phage-host interactions in Lactococcus lactis
Hélène Deveau1, Marie-Rose Van Calsteren, Sylvain Moineau
1Département de Biochimie et de Microbiologie, Faculté des Sciences et de Génie, Groupe de Recherche en Ecologie Buccale (GREB), Faculté de Médecine Dentaire, Université Laval, Québec, Canada G1K 7P4.
Applied and Environmental Microbiology
|August 30, 2002
Summary
Lactococcus lactis strains producing exopolysaccharides (EPS) are sensitive to specific phages. Phage infection is not dependent on EPS production or composition, challenging previous assumptions about phage resistance in these bacteria.
Area of Science:
- Microbiology
- Bacteriology
- Virology
Background:
- Lactococcus lactis is a key bacterium in dairy fermentation.
- Exopolysaccharides (EPS) produced by L. lactis can influence bacterial properties.
- Phage infections pose a significant threat to dairy starter cultures.
Purpose of the Study:
- To investigate the susceptibility of exopolysaccharide-producing (Eps+) Lactococcus lactis strains to lytic phages.
- To determine if EPS production or composition influences phage sensitivity.
- To elucidate the role of EPS in phage resistance mechanisms.
Main Methods:
- Isolation and characterization of lytic phages from buttermilk.
- Multiplex PCR for phage species classification.
- Host range determination of isolated phages against Eps+ and Eps- L. lactis strains.
- Monosaccharide composition analysis of EPS.
- Plasmid curing experiments and phage adsorption assays.
Main Results:
- Eight novel lytic phages (Q61-Q68) were isolated, belonging to the 936 species.
- Phages specifically infected two Eps+ strains (SMQ-419 and SMQ-420), with no infection observed in other Eps+ or all Eps- strains.
- EPS composition varied among strains but did not correlate with phage sensitivity.
- EPS production was not essential for phage infection, and EPS did not confer significant phage resistance.
Conclusions:
- Virulent phages can infect exopolysaccharide-producing Lactococcus lactis strains.
- Phage sensitivity in L. lactis is not directly mediated by the presence or composition of exopolysaccharides.
- The study challenges the notion that EPS production confers phage resistance in L. lactis.