27 research outputs found
P087, a lactococcal phage with a morphogenesis module similar to an Enterococcus faecalis prophage
The virulent lactococcal phage P087 was isolated from a dairy environment in 1978. This phage was then
recognized as the reference member for one of the ten phage groups currently known to infect Lactococcus
lactis strains. The double-stranded DNA genome of this Siphoviridae phage is composed of 60,074 bp and is
circularly permuted. Five tRNA and 88 orfs were found within an uncommon genome architecture. Eleven
structural proteins were also identified through SDS-PAGE and LC-MS/MS analyses. Of note, 11 translated orfs
from the structural module of phage P087 have identities to gene products found in a prophage located in the
genome of Enterococcus faecalis V583. The alignment of both genomic sequences suggests that DNA
exchanges could occur between these two phages which are infecting low G+C bacteria found in similar
ecological niches
CRISPR provides acquired resistance against viruses in prokaryotes
Clustered regularly interspaced short palindromic repeats (CRISPR) are a distinctive feature of the genomes of most Bacteria and Archaea and are thought to be involved in resistance to bacteriophage. We found that following viral challenge, bacteria integrated new spacers derived from phage genomic sequences. Removal or addition of particular spacers modified the phage-resistance phenotype of the cell. Thus, CRISPR, together with associated cas genes, provided resistance against phages, whereby specificity is determined by spacer/phage sequence similarity
The diversity-generating benefits of a prokaryotic adaptive immune system
Published onlineJOURNAL ARTICLEProkaryotic CRISPR-Cas adaptive immune systems insert spacers derived from viruses and other parasitic DNA elements into CRISPR loci to provide sequence-specific immunity. This frequently results in high within-population spacer diversity, but it is unclear if and why this is important. Here we show that, as a result of this spacer diversity, viruses can no longer evolve to overcome CRISPR-Cas by point mutation, which results in rapid virus extinction. This effect arises from synergy between spacer diversity and the high specificity of infection, which greatly increases overall population resistance. We propose that the resulting short-lived nature of CRISPR-dependent bacteria-virus coevolution has provided strong selection for the evolution of sophisticated virus-encoded anti-CRISPR mechanisms.S.v.H. has received funding from the European Unionâs Horizon 2020 research and innovation programme under the Marie SkĆodowska-Curie grant agreement number 660039. E.R.W. received funding from the People Programme (Marie Curie Actions) of the European Unionâs Seventh Framework Programme (FP7/2007-2013) under Research Executive Agency grant agreement number 327606. E.R.W., A.B. and M.B. also acknowledge the Natural Environment Research Council, the Biotechnology and Biological Sciences Research Council, the Royal Society, the Leverhulme Trust, the Wellcome Trust and the AXA research fund for funding. J.M.B.-D. was supported by the University of California San Francisco Program for Breakthrough in Biomedical Research, the Sandler Foundation, and a National Institutes of Health Directorâs Early Independence Award (DP5-OD021344). H.C. was funded by the Erasmus+ programme (European Union), the ExploraâSup programme (RĂ©gion RhĂŽne-Alpes) and the Centre RĂ©gional des Ćuvres Universitaires et Scolaires (CROUS; French State)
Technical note : use of RFLP to characterize Lactococcus lactis strains producing exopolysaccharides
Restriction fragment length polymorphism (RFLP) is
used to differentiate microorganisms by analysis of
their DNA restriction patterns. A modified RFLP procedure is proposed for the rapid characterization of Lactococcus lactis strains producing exopolysaccharides
(EPS). The availability of such effective cataloging system is likely to benefit research aimed at identifying
lactococcal strains that produce novel EPS
CRISPR/Cas system and its role in phage-bacteria interactions
Clustered regularly interspaced short palindromic repeats (CRISPRs)
along with Cas proteins is a widespread system across bacteria and
archaea that causes interference against foreign nucleic acids. The
CRISPR/Cas system acts in at least two general stages: the adaptation
stage, where the cell acquires new spacer sequences derived from foreign DNA, and the interference stage, which uses the recently acquired
spacers to target and cleave invasive nucleic acid. The CRISPR/Cas system participates in a constant evolutionary battle between phages and
bacteria through addition or deletion of spacers in host cells and mutations or deletion in phage genomes. This review describes the recent
progress made in this fast-expanding field
Phage resistance in lactic acid bacteria
Lactic Acid Bacteria (LAB) are used in a variety of industrial fermentation processes
because of their ability to convert a variety of substrates into complex products. Any
technological process that relies on bacterial fermentation is vulnerable to bacteriophage
infections. This chapter describes the relationship between bacteriophages and their LAB
hosts in the context of the food fermentation industry. Specifically, we highlight the most
significant antiviral mechanisms in LAB. The primary focus will be given to LAB used
by the dairy industry because it has openly acknowledged the problem of phage
infections and has teamed up with academia and starter cultures companies to develop
natural and engineered phage resistance systems to curtail the propagation of diverse
phages
Effect of Exopolysaccharides on Phage-Host Interactions in Lactococcus lactis
In this study, we report that Lactococcus lactis strains producing exopolysaccharides (EPS) are sensitive to virulent phages. Eight distinct lytic phages (Q61 to Q68) specifically infecting Eps(+) strains were isolated in 47 buttermilk samples obtained from 13 North American factories. The eight phages were classified within the 936 species by the multiplex PCR method, indicating that these phages are not fundamentally distinct from those infecting Eps(â) L. lactis strains. The host range of these phages was determined with 19 Lactococcus strains, including 7 Eps(+) and 12 Eps(â) cultures. Three phages (Q62, Q63, and Q64) attacked only the Eps(+) strain SMQ-419, whereas the five other phages (Q61, Q65, Q66, Q67, and Q68) infected only the Eps(+) strain SMQ-420. The five other Eps(+) strains (H414, MLT2, MLT3, SMQ-461, and SMQ-575) as well as the 12 Eps(â) strains were insensitive to these phages. The monosaccharide composition of the polymer produced by the seven Eps(+) strains was determined. The EPS produced by strains MLT3, SMQ-419, and SMQ-575 contained glucose, galactose, and rhamnose. The EPS fabricated by H414 contained only galactose. The EPS made by MLT2, SMQ-420, and SMQ-461 contained glucose and galactose. These findings indicate that the sugar composition of the EPS has no effect on phage sensitivity. The plasmid encoding the eps operon was cured from the two phage-sensitive strains. The cured derivatives were still phage sensitive, which indicates that EPS are not necessary for phage infection. Phage adsorption assays showed that the production of EPS does not confer a significant phage resistance phenotype