Changes in Escherichia coli to enteric protozoa ratios in rivers: Implications for risk-based assessment of drinking water treatment requirements.

Minimum treatment requirements are set in response to established or anticipated levels of enteric pathogens in the source water of drinking water treatment plants (DWTPs). For surface water, contamination can be determined directly by monitoring reference pathogens or indirectly by measuring fecal indicators such as Escherichia coli (E. coli).

Importance of Distributional Forms for the Assessment of Protozoan Pathogens Concentrations in Drinking-Water Sources.

The identification of appropriately conservative statistical distributions is needed to predict microbial peak events in drinking water sources explicitly. In this study, Poisson and mixed Poisson distributions with different upper tail behaviors were used for modeling source water Cryptosporidium and Giardia data from 30 drinking water treatment plants. Small differences (<0.

Impact of Hydrometeorological Events for the Selection of Parametric Models for Protozoan Pathogens in Drinking-Water Sources.

Temporal variations in concentrations of pathogenic microorganisms in surface waters are well known to be influenced by hydrometeorological events. Reasonable methods for accounting for microbial peaks in the quantification of drinking water treatment requirements need to be addressed. Here, we applied a novel method for data collection and model validation to explicitly account for weather events (rainfall, snowmelt) when concentrations of pathogens are estimated in source water.

Energy Conservation and the Promotion of Legionella pneumophila Growth: The Probable Role of Heat Exchangers in a Nosocomial Outbreak.

OBJECTIVE To determine the source of a Legionella pneumophila serogroup 5 nosocomial outbreak and the role of the heat exchanger installed on the hot water system within the previous year. SETTING A 400-bed tertiary care university hospital in Sherbrooke, Canada. METHODS Hot water samples were collected and cultured for L.

Adaptation in bacterial CRISPR-Cas immunity can be driven by defective phages.

Clustered regularly interspaced short palindromic repeats (CRISPRs) and their associated cas genes serve as a prokaryotic 'adaptive' immune system, protecting against foreign DNA elements such as bacteriophages. CRISPR-Cas systems function by incorporating short DNA 'spacers', homologous to invading DNA sequences, into a CRISPR array (adaptation). The array is then transcribed and matured into RNA molecules (maturation) that target homologous DNA for cleavage (interference).

Inactivation of dairy bacteriophages by commercial sanitizers and disinfectants.

Many commercial sanitizers and disinfectants have been used over the years to control microbial contamination but their efficacy on phages is often unknown. Here, 23 commercial chemical products, including 21 food-grade sanitizers were tested against virulent dairy phages. These food-grade chemicals included oxidizing agents, halogenated agents, alcohols, quaternary ammonium compounds, anionic acids, iodine-based acids, and an amphoteric chemical.

CRISPR-Cas and restriction-modification systems are compatible and increase phage resistance.

Bacteria have developed a set of barriers to protect themselves against invaders such as phage and plasmid nucleic acids. Different prokaryotic defence systems exist and at least two of them directly target the incoming DNA: restriction-modification (R-M) and CRISPR-Cas systems. On their own, they are imperfect barriers to invasion by foreign DNA.

The double-edged sword of CRISPR-Cas systems.

A recent paper gives the details on how specific small RNAs can program a protein to cleave an undesired piece of DNA and to provide immunity to a microbial cell.

Involvement of the major capsid protein and two early-expressed phage genes in the activity of the lactococcal abortive infection mechanism AbiT.

The dairy industry uses the mesophilic, Gram-positive, lactic acid bacterium (LAB) Lactococcus lactis to produce an array of fermented milk products. Milk fermentation processes are susceptible to contamination by virulent phages, but a plethora of phage control strategies are available. One of the most efficient is to use LAB strains carrying phage resistance systems such as abortive infection (Abi) mechanisms.

A reverse transcriptase-related protein mediates phage resistance and polymerizes untemplated DNA in vitro.

Reverse transcriptases (RTs) are RNA-dependent DNA polymerases that usually function in the replication of selfish DNAs such as retrotransposons and retroviruses. Here, we have biochemically characterized a RT-related protein, AbiK, which is required for abortive phage infection in the Gram-positive bacterium Lactococcus lactis. In vitro, AbiK does not exhibit the properties expected for an RT, but polymerizes long DNAs of 'random' sequence, analogous to a terminal transferase.

The CRISPR/Cas bacterial immune system cleaves bacteriophage and plasmid DNA.

Bacteria and Archaea have developed several defence strategies against foreign nucleic acids such as viral genomes and plasmids. Among them, clustered regularly interspaced short palindromic repeats (CRISPR) loci together with cas (CRISPR-associated) genes form the CRISPR/Cas immune system, which involves partially palindromic repeats separated by short stretches of DNA called spacers, acquired from extrachromosomal elements. It was recently demonstrated that these variable loci can incorporate spacers from infecting bacteriophages and then provide immunity against subsequent bacteriophage infections in a sequence-specific manner.

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.

Bacteriophages of lactobacillus.

In this review, we are listing Lactobacillus phages that have been reported in peer-reviewed articles published since 1960. Putative phages that are defective or have not been shown to be infectious, such as phage-like particles, are not discussed. Our literature searches led to the identification of 231 Lactobacillus phages, 186 of which have been observed by electron microscopy, with 109 belonging to the Siphoviridae family, 76 to the Myoviridae family, and 1 to the Podoviridae family.

Crystal structure of ORF12 from Lactococcus lactis phage p2 identifies a tape measure protein chaperone.

We report here the characterization of the nonstructural protein ORF12 of the virulent lactococcal phage p2, which belongs to the Siphoviridae family. ORF12 was produced as a soluble protein, which forms large oligomers (6- to 15-mers) in solution. Using anti-ORF12 antibodies, we have confirmed that ORF12 is not found in the virion structure but is detected in the second half of the lytic cycle, indicating that it is a late-expressed protein.

The XerC recombinase of Proteus mirabilis: characterization and interaction with other tyrosine recombinases.

XerC and XerD are two site-specific recombinases, which act on different sites to maintain replicons in a monomeric state. This system, which was first discovered and studied in Escherichia coli, is present in several species including Proteus mirabilis, where the XerD recombinase was previously characterized by our laboratory. In this paper, we report the presence of the xerC gene in P.