Spread and variability of the integrase gene in Lactobacillus delbrueckii ssp. lactis strains and phages isolated from whey starter cultures

Exploring the diversity of bacteriophage specific to Oenococcus oeni and Lactobacillus spp and their role in wine production

The widespread existence of bacteriophage has been of great interest to the biological research community and ongoing investigations continue to explore their diversity and role. They have also attracted attention and in-depth research in connection to fermented food processing, in particular from the dairy and wine industries. Bacteriophage, mostly oenophage, may in fact be a 'double edged sword' for winemakers: whilst they have been implicated as a causal agent of difficulties with malolactic fermentation (although not proven), they are also beginning to be considered as alternatives to using sulphur dioxide to prevent wine spoilage. Investigation and characterisation of oenophage of Oenococcus oeni, the main species used in winemaking, are still limited compared to lactococcal bacteriophage of Lactococcus lactis and Lactiplantibacillus plantarum (formally Lactobacillus plantarum), the drivers of most fermented dairy products. Interestingly, these strains are also being used or considered for use in winemaking. In this review, the genetic diversity and life cycle of phage, together with the debate on the consequent impact of phage predation in wine, and potential control strategies are discussed. KEY POINTS: • Bacteriophage detected in wine are diverse. • Many lysogenic bacteriophage are found in wine bacteria. • Phage impact on winemaking can depend on the stage of the winemaking process. • Bacteriophage as potential antimicrobial agents against spoilage organisms.

Phage-Host Interactions of Cheese-Making Lactic Acid Bacteria

Cheese production is a global biotechnological practice that is reliant on robust and technologically appropriate starter and adjunct starter cultures to acidify the milk and impart particular flavor and textural properties to specific cheeses. To this end, lactic acid bacteria, including Lactococcus lactis, Streptococcus thermophilus, and Lactobacillus and Leuconostoc spp., are routinely employed. However, these bacteria are susceptible to infection by (bacterio)phages. Over the past decade in particular, significant advances have been achieved in defining the receptor molecules presented by lactococcal host bacteria and in the structural analysis of corresponding phage-encoded receptor-binding proteins. These lactococcal model systems are expanding toward understanding phage-host interactions of other LAB species. Ultimately, such scientific efforts will uncover the mechanistic (dis)similarities among these phages and define how these phages recognize and infect their hosts. This review presents the current status of the LAB-phage interactome, highlighting the most recent and significant developments in this active research field.

Molecular characterization of three Lactobacillus delbrueckii subsp. bulgaricus phages

In this study, three phages infecting Lactobacillus delbrueckii subsp. bulgaricus, named Ld3, Ld17, and Ld25A, were isolated from whey samples obtained from various industrial fermentations. These phages were further characterized in a multifaceted approach: (i) biological and physical characterization through host range analysis and electron microscopy; (ii) genetic assessment through genome analysis; (iii) mass spectrometry analysis of the structural components of the phages; and (iv), for one phage, transcriptional analysis by Northern hybridization, reverse transcription-PCR, and primer extension. The three obtained phage genomes display high levels of sequence identity to each other and to genomes of the so-called group b L. delbrueckii phages c5, LL-Ku, and phiLdb, where some of the observed differences are believed to be responsible for host range variations.

Lactobacillus plantarum bacteriophages isolated from Kefir grains: phenotypic and molecular characterization

Two greatly related Lactobacillus plantarum bacteriophages (named FAGK1 and FAGK2) were isolated from Kefir grains of different origins. Both phages belonged to the Siphoviridae family (morphotype B1) and showed similar dimensions for head and tail sizes. The host range of the two phages, using 36 strains as potential host strains, differed only in the phage reactivity against one of them. The phages showed latent periods of 30 min, burst periods of 80+/-10 min and burst size values of 11.0+/-1.0 PFU per infected cell as mean value. Identical DNA restriction patterns were obtained for both phages with PvuI, SalI, HindIII and MluI. The viral DNA apparently did not present extremes cos and the structural protein patterns presented four major bands (32.9, 35.7, 43.0 and 66.2 kDa). This study reports the first isolation of bacteriophages of Lb. plantarum from Kefir grains and adds further knowledge regarding the complex microbial community of this fermented milk.

Lysogeny in Lactobacillus delbrueckii strains and characterization of two new temperate prolate-headed bacteriophages

AIMS

Frequency of lysogeny in Lactobacillus delbrueckii strains (from commercial and natural starters) and preliminary characterization of temperate bacteriophages isolated from them.

METHODS AND RESULTS

Induction of strains (a total of 16) was made using mitomycin C (MC) (0.5 mug ml(-1)). For 37% of the MC-treated supernatants, it was possible to detect phage particles or presence of killing activity, but only two active bacteriophages were isolated. The two temperate phages isolated were prolate-headed phages which belonged to group c of Lact. delbrueckii bacteriophages classification. Different DNA restriction patterns were obtained for each phage, while the structural protein profiles and packaging sites were identical. Distinctive one-step growth curves were exhibited by each phage. An influence of calcium ions was observed for their lysis in broth but not on the adsorption levels.

CONCLUSIONS

Our study showed that lysogeny is also present in Lact. delbrueckii strains, including commercial strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

Commercial strains could be lysogenic and this fact has a great practical importance since they could contribute to the dissemination of active-phage particles in industrial environments.

Detection and identification ofLactobacillus helveticusbacteriophages by PCR

A PCR protocol for detection ofLactobacillus helveticusbacteriophages was optimized. PCR was designed taking into account the sequence of thelysgene of temperate bacteriophage Φ-0303 and optimized to obtain a fragment of 222 bp using differentLb. helveticusphages from our collection. PCR was applied to total phage DNA extracted from 53 natural whey starters used for the production of Grana cheese and all gave the expected fragment. The presence of actively growing phages in the cultures was verified by traditional tests. Several PCR products of thelysgene were sequenced and aligned. The resulting sequences showed variable heterogeneity between the phages.