The major proteins of phage TP901-1 virion were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and structural relations were determined using specific antibodies, obtained by affinity purification from a... more
The major proteins of phage TP901-1 virion were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and structural relations were determined using specific antibodies, obtained by affinity purification from a polyclonal serum. A 23-kDa protein was identified as the major tail protein, and a 31-kDa molecule as the major head protein, respectively. Labeling experiments with antibodies against two proteins, with molecular masses of 20 and 19 kDa, indicated that they were baseplate-related components. A 72-kDa protein was found to be part of a neck passage structure, which includes a collar. Evidence for the presence of attached whiskers was also obtained. T7 RNA polymerase-mediated expression of the two major proteins confirmed the gene location of the previously sequenced region of the phage genome. The relation to other lactococcal phages was determined by DNA hybridization and antibody probing, showing that despite low DNA similarity, TP901-1 NPS epitopes were...
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Ropy Streptococcus (Lactococcus) cremoris strains isolated from a ropy Swedish sour milk ("longfil") and a ropy Finnish milk product ("Viili") were screened for their plasmid-encoded functions. Curing... more
Ropy Streptococcus (Lactococcus) cremoris strains isolated from a ropy Swedish sour milk ("longfil") and a ropy Finnish milk product ("Viili") were screened for their plasmid-encoded functions. Curing experiments strongly indicated that the ropy phenotype was linked to a 17-Md plasmid in the Swedish strains and to a 30 Md plasmid in the Finnish strains. Comparative restriction endonuclease analysis and DNA/DNA-hybridization studies revelated that plasmids from both strain families shared homologous DNA regions. Though be Swedish ropy strains harbored a conjugative 45-Md lactose plasmid, no cotransfer of the 17 Md plasmid occurred.
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Lipoproteins of temperate phage are a broad family of membrane proteins encoded in the lysogeny module of temperate phages. Expression of the ltp(TP-J34) gene of temperate Streptococcus thermophilus phage TP-J34 interferes with phage... more
Lipoproteins of temperate phage are a broad family of membrane proteins encoded in the lysogeny module of temperate phages. Expression of the ltp(TP-J34) gene of temperate Streptococcus thermophilus phage TP-J34 interferes with phage infection at the stage of triggering DNA release and injection into the cell. Here, we report the first structure of a superinfection exclusion protein. We have expressed and determined the X-ray structure of Ltp(TP-J34). The soluble domain of Ltp(TP-J34) is composed of a tandem of three-helix helix-turn-helix (HTH) domains exhibiting a highly negatively charged surface. By isolating mutants of lactococcal phage P008wt with reduced sensitivities to Ltp(TP-J34) and by genome sequencing of such mutants we obtained evidence supporting the notion that Ltp(TP-J34) targets the phage's tape measure protein (TMP) and blocks its insertion into the cytoplasmic membrane.
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Nine Lactococcus lactis c2 phages propagated on different hosts were screened for thermal resistance in skimmed milk. Pronounced variations in thermal resistance were found. Three phages displayed high sensitivity towards heat resulting... more
Nine Lactococcus lactis c2 phages propagated on different hosts were screened for thermal resistance in skimmed milk. Pronounced variations in thermal resistance were found. Three phages displayed high sensitivity towards heat resulting in >8 log reductions after 70 °C for 5 min, whereas the most thermal resistant phages required 80 °C for 5 min to obtain the same reduction. Inactivation kinetics were determined for
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We show by electron microscopy that Lactobacillus gasseri phage LgaI, a temperate phage residing in the chromosome of Lactobacillus gasseri ATCC33323, belongs to the family of Myoviridae phages. The LgaI DNA is packed by the... more
We show by electron microscopy that Lactobacillus gasseri phage LgaI, a temperate phage residing in the chromosome of Lactobacillus gasseri ATCC33323, belongs to the family of Myoviridae phages. The LgaI DNA is packed by the "head-full" mechanism, as demonstrated by analysis of restriction patterns of heated (74 degrees C) or non-heated DNA. By isolating prophage-cured cells, we were able to demonstrate phage LgaI to be responsible for the strong autolytic phenotype observed for Lactobacillus gasseri ATCC33323. In addition, we show that a copy of the LgaI prophage resides in the chromosome of Lactobacillus gasseri NCK102. The LgaI prophage was not inducible in L. gasseri NCK102-adh by mitomycin C, however, it apparently contributed to the autolytic phenotype of this strain.
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Research Interests: Electron Microscopy, Comparative Genomics, Bacteriophages, Morphology, Multidisciplinary, and 14 moreGenetic Diversity, Virus, Applied Environmental Microbiology, Bacteria, Streptococcus Pyogenes, Tandem Mass Spectrometry, Genome, Liquid Chromatography, Genome sequence, Host Range, Open Reading Frame, Proteome, Lactococcus lactis, and DNA probes
This paper presents research on the effect of enzymatic cross-linking of milk proteins on the properties of yoghurt. Whole milk was incubated with transglutaminase (TG) prior to fermentation (2 h, 40°C, E/S ratio 1/2000). Enzyme action... more
This paper presents research on the effect of enzymatic cross-linking of milk proteins on the properties of yoghurt. Whole milk was incubated with transglutaminase (TG) prior to fermentation (2 h, 40°C, E/S ratio 1/2000). Enzyme action was stopped by heating (1 min, 80°C). Skim-milk ...
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Lactoccocus lactis is a Gram-positive bacterium widely used in the dairy industry in the production of an array of cheeses and other fermented milk products. Here, we describe the sequencing and genome annotations of a set of four phages... more
Lactoccocus lactis is a Gram-positive bacterium widely used in the dairy industry in the production of an array of cheeses and other fermented milk products. Here, we describe the sequencing and genome annotations of a set of four phages virulent to L. lactis and exhibiting similarities to phage 1706.
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Lipoprotein Ltp encoded by temperate Streptococcus thermophilus phage TP-J34 is the prototype of the wide-spread family of host cell surface-exposed lipoproteins involved in superinfection exclusion (sie). When screening for other S.... more
Lipoprotein Ltp encoded by temperate Streptococcus thermophilus phage TP-J34 is the prototype of the wide-spread family of host cell surface-exposed lipoproteins involved in superinfection exclusion (sie). When screening for other S. thermophilus phages expressing this type of lipoprotein, three temperate phages-TP-EW, TP-DSM20617, and TP-778-were isolated. In this communication we present the total nucleotide sequences of TP-J34 and TP-778L. For TP-EW, a phage almost identical to TP-J34, besides the ltp gene only the two regions of deviation from TP-J34 DNA were analyzed: the gene encoding the tail protein causing an assembly defect in TP-J34 and the gene encoding the lysin, which in TP-EW contains an intron. For TP-DSM20617 only the sequence of the lysogeny module containing the ltp gene was determined. The region showed high homology to the same region of TP-778. For TP-778 we could show that absence of the attR region resulted in aberrant excision of phage DNA. The amino acid se...
Bacteria assigned to the genus Weissella are Gram-positive, catalase-negative, non-endospore forming cells with coccoid or rod-shaped morphology (Collins et al., 1993; Björkroth et al., 2009, 2014) and belong to the group of bacteria... more
Bacteria assigned to the genus Weissella are Gram-positive, catalase-negative, non-endospore forming cells with coccoid or rod-shaped morphology (Collins et al., 1993; Björkroth et al., 2009, 2014) and belong to the group of bacteria generally known as lactic acid bacteria. Phylogenetically, the Weissella belong to the Firmicutes, class Bacilli, order Lactobacillales and family Leuconostocaceae (Collins et al., 1993). They are obligately heterofermentative, producing CO2 from carbohydrate metabolism with either d(-)-, or a mixture of d(-)- and l(+)- lactic acid and acetic acid as major end products from sugar metabolism. To date, there are 19 validly described Weissella species known. Weissella spp. have been isolated from and occur in a wide range of habitats, e.g., on the skin and in the milk and feces of animals, from saliva, breast milk, feces and vagina of humans, from plants and vegetables, as well as from a variety of fermented foods such as European sourdoughs and Asian and ...
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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... more
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.