Occurrence Of Bacteriophages Research Articles

Detection of lytic phage infecting flavour-producing strain of Lacticaseibacillus paracasei in the dairy effluents of Kerala.

The performance of the starter culture is a critical factor that decides the quality of fermented milk. Dahi is a fermented milk product popular in India made using a mixed starter culture of lactic acid bacteria comprising acid and flavour producers. The prevalence of bacteriophages in the dairy environment can critically affect the activity of these starter cultures resulting in starter failure. As there is little information available on the occurrence of bacteriophages in the dairy environment of Kerala, this research communication examines the presence of lytic bacteriophages acting against three potential flavour-producing strains of Lacticaseibacillus paracasei (Lc. paracasei). Dairy effluent samples were screened for the presence of phages against the strains of Lc. paracasei by the multiple host enrichment method. Plates showing clearance zone in spot assay were confirmed for the presence of phages by double-layer agar assay. The plaques obtained in the double-layer agar assay were purified for further identification by next-generation sequencing. A bacteriophage infecting one of the three strains of Lc. paracasei was detected by the plaque assay and the blast annotation of the bacteriophage sequence found 86.05% similarity of the phage to Siphoviridae family. The study endorses the need for monitoring phages in the dairy environment to control phage-related starter failure in the state of Kerala.

Microbial community dynamics in thermophilic undefined milk starter cultures

Model undefined thermophilic starter cultures were produced from raw milk of nine pasta-filata cheesemaking plants using a selective procedure based on pasteurization and incubation at high temperature with the objective of studying the microbial community dynamics and the variability in performances under repeated (7–13) reproduction cycles with backslopping. The traditional culture-dependent approach, based on random isolation and molecular characterization of isolates was coupled to the determination of pH and the evaluation of the ability to produce acid and fermentation metabolites. Moreover, a culture-independent approach based on amplicon-targeted next-generation sequencing was employed. The microbial diversity was evaluated by 16S rRNA gene sequencing (V1–V3 regions), while the microdiversity of Streptococcus thermophilus populations was explored by using novel approach based on sequencing of partial amplicons of the phosphoserine phosphatase gene (serB). In addition, the occurrence of bacteriophages was evaluated by qPCR and by multiplex PCR. Although it was relatively easy to select for a community dominated by thermophilic lactic acid bacteria (LAB) within a single reproduction cycle, final pH, LAB populations and acid production activity fluctuated over reproduction cycles. Both culture-dependent and -independent methods showed that the cultures were dominated by either S. thermophilus or Lactobacillus delbrueckii subsp. lactis or by both species. Nevertheless, subdominant mesophilic species, including lactococci and spoilage organisms, persisted at low levels. A limited number of serB sequence types (ST) were present in S. thermophilus populations. L. delbrueckii and Lactococcus lactis bacteriophages were below the detection limit of the method used and high titres of cos type S. thermophilus bacteriophages were detected in only two cases. In one case a high titre of bacteriophages was concurrent with a S. thermophilus biotype shift in the culture.This study largely confirms previous data on the composition of undefined thermophilic starters used for the production of traditional cheeses in Italy but it is the first one to systematically address the dynamics of the cultures under a repeated reproduction regime with backslopping.

Bacteriophage therapy revisited

Phage therapy is a natural process of treating the bacterial infections of animals, plants and humans and it was used before the discovery and widespread of antibiotics. Even now this technology is widely used to increase the shelf life of fruits, vegetables, meat and harvested plants. In this mini review paper, we briefly describe the natural occurrence of bacteriophages; their discovery, history, emergence of phage therapy in the light of antibiotic resistance and their advantages over the traditional antibiotics. Preclinical studies of phage therapy in experimental animals/plants and its applications on the infectious diseases; wound infections emerged by the antibiotic resistant bacteria. Bacteriophage was first discovered by Ernest Hankin in 1896 from the water of Jumna river containing antibacterial substances which limited the spread of Cholera epidemics. In the initial stage of phage therapy, there were problems with the technology and now all these problems have been resolved by the advancement of science and technology. Now based on recent experience and results of bacteriophage applications against bacterial infections, this innovative technology for the treatment of various antibiotic resistant infections is successful. Key words: Bacteriophage, phage therapy, food preservation, bacteriophage history, bacteriophage in agriculture, phage therapy human health

The occurrence of bacteriophages in spirit vinegar fermentation

Bacteriophages in concentrations of approximately 108–109 particles/ml were demonstrated in culture lysates of industrial submerged spirit vinegar fermentations running in different European vinegar factories. Besides frequently found fragments of phages, two types of phages could be described. The frequent type I seems to belong to Bradley-group A; type II, with a remarkably larger head, may belong to group C. For simulation in the laboratory a phage-contaminated industrial culture was kept over 102 charges (time of cycle 24->240 h) in a semicontinuously operated 8-1 fermentor. A close relationship between spontaneous breakdowns and phage occurrence exists. Discrimination of breakdowns caused by lack of ethanol could not be made. Attempts to establish a bioassay for the phages failed presumably because of the instability of the phages. Continuing cultivation and waiting for secondary growth finally results in stable and productive fermentation.

The occurrence of bacteriophages in the rumen and their influence on rumen bacterial populations.

Se han demostrado que dos cultivos de bacterias de rumen (un baston gram negativo, designado W461, y una cepa de ovalos deEadie) estan infectados con bacteriofagos. El bacteriofago de W461 es templado; aquel de los ovalos es virulento y depleta rapidamente la poblacion bacteriana en vivo.