Lactic acid-producing bacteria are associated with various plant and animal niches and play a key role in the production of fermented foods and beverages. We report nine genome sequences representing the phylogenetic and functional diversity of these bacteria. The small genomes of lactic acid bacteria encode a broad repertoire of transporters for efficient carbon and nitrogen acquisition from the nutritionally rich environments they inhabit and reflect a limited range of biosynthetic capabilities that indicate both prototrophic and auxotrophic strains. Phylogenetic analyses, comparison of gene content across the group, and reconstruction of ancestral gene sets indicate a combination of extensive gene loss and key gene acquisitions via horizontal gene transfer during the coevolution of lactic acid bacteria with their habitats. evolutionary genomics ͉ fermentation L actic acid bacteria (LAB) are historically defined as a group of microaerophilic, Gram-positive organisms that ferment hexose sugars to produce primarily lactic acid. This functional classification includes a variety of industrially important genera, including Lactococcus, Enterococcus, Oenococcus, Pediococcus, Streptococcus, Leuconostoc, and Lactobacillus species. The seemingly simplistic metabolism of LAB has been exploited throughout history for the preservation of foods and beverages in nearly all societies dating back to the origins of agriculture (1). Domestication of LAB strains passed down through various culinary traditions and continuous passage on food stuffs has resulted in modern-day cultures able to carry out these fermentations. Today, LAB play a prominent role in the world food supply, performing the main bioconversions in fermented dairy products, meats, and vegetables. LAB also are critical for the production of wine, coffee, silage, cocoa, sourdough, and numerous indigenous food fermentations (2).LAB species are indigenous to food-related habitats, including plant (fruits, vegetables, and cereal grains) and milk environments. In addition, LAB are naturally associated with the mucosal surfaces of animals, e.g., small intestine, colon, and vagina. Isolates of the same species often are obtained from plant, dairy, and animal habitats, implying wide distribution and specialized adaptation to these diverse environments. LAB species employ two pathways to metabolize hexose: a homofermentative pathway in which lactic acid is the primary product and a heterofermentative pathway in which lactic acid, CO 2 , acetic acid, and͞or ethanol are produced (3).Complete genome sequences have been published for eight fermentative and commensal LAB species: Lactococcus lactis, Lactobacillus plantarum, Lactobacillus johnsonii, Lactobacillus acidophilus, Lactobacillus sakei, Lactobacillus bulgaricus, Lactobacillus salivarius, and Streptococcus thermophilus (4-11). This study examines nine other LAB genomes representing the phylogenetic and functional diversity of lactic acid-producing microorganisms. The LAB have small genomes encoding a range of biosynthe...

Background: Bifidobacteria are frequently proposed to be associated with good intestinal health primarily because of their overriding dominance in the feces of breast fed infants. However, clinical feeding studies with exogenous bifidobacteria show they don't remain in the intestine, suggesting they may lose competitive fitness when grown outside the gut.

Campylobacter jejuni continues to be the leading cause of bacterial food-borne illness worldwide, so improvements to current methods used for bacterial detection and disease prevention are needed. We describe here the genome and proteome of C. jejuni bacteriophage NCTC 12673 and the exploitation of its receptor-binding protein for specific bacterial detection. Remarkably, the 135-kb Myoviridae genome of NCTC 12673 differs greatly from any other proteobacterial phage genome described (including C. jejuni phages CP220 and CPt10) and instead shows closest homology to the cyanobacterial T4-related myophages. The phage genome contains 172 putative open reading frames, including 12 homing endonucleases, no visible means of packaging, and a putative trans-splicing intein. The phage DNA appears to be strongly associated with a protein that interfered with PCR amplification and estimation of the phage genome mass by pulsed-field gel electrophoresis. Identification and analyses of the receptor-binding protein (Gp48) revealed features common to the Salmonella enterica P22 phage tailspike protein, including the ability to specifically recognize a host organism. Bacteriophage receptor-binding proteins may offer promising alternatives for use in pathogen detection platforms.Campylobacter belongs to the epsilon class of proteobacteria and is the leading cause of bacterial food-borne gastroenteritis worldwide (22). Campylobacter has also been associated with severe neurological disorders such as the Guillain-Barré and Miller-Fisher syndromes, as well as reactive arthritis and irritable bowel syndrome (32). Many Campylobacter phages have been characterized by their host-range characteristics, morphology, genome size, and susceptibility to restriction endonucleases (5,7,24). Only a few of the characterized Campylobacter phages are members of the B1 group of the family Siphoviridae (1), while most belong to the family Myoviridae possessing genomes which fall into three size classes: 110 to 150 kb (class III), 170 to 190 kb (class II), and 320 kb (class I) (24). One interesting characteristic of many of these phages is that their DNA appears to be resistant to cleavage by several common restriction endonucleases, thus making them "refractory to genomic analysis" (34). Two genomes of Campylobacter phages have been sequenced thus far: CPt10 and CP220 (34). Both appear to be closely related to each other and belong to the class II of Campylobacter Myoviridae phage genomes (34).Bacteriophages possess enormous diagnostic and therapeutic potential, which provides promise for the development of a wide range of novel antimicrobials and diagnostic tools (14). Numerous phages have been isolated against Campylobacter for use in phage typing schemes (9,10,12,18,25), but it has only recently been shown that bacteriophages can effectively decrease Campylobacter contamination (4, 20, 36). For example, Campylobacter-specific phages were able to reduce the numbers of Campylobacter coli and Campylobacter jejuni in chickens when added directly to the...

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Helix-hairpin-helix (HhH) is a widespread motif involved in sequence-nonspecific DNA binding. The majority of HhH motifs function as DNA-binding modules with typical occurrence of one HhH motif or one or two (HhH)2 domains in proteins. We recently identified 24 HhH motifs in DNA topoisomerase V (Topo V). Although these motifs are dispensable for the topoisomerase activity of Topo V, their removal narrows the salt concentration range for topoisomerase activity tenfold. Here, we demonstrate the utility of Topo V's HhH motifs for modulating DNA-binding properties of the Stoffel fragment of TaqDNA polymerase and Pfu DNA polymerase. Different HhH cassettes fused with either NH2 terminus or COOH terminus of DNA polymerases broaden the salt concentration range of the polymerase activity significantly (up to 0.5 M NaCl or 1.8 M potassium glutamate). We found that anions play a major role in the inhibition of DNA polymerase activity. The resistance of initial extension rates and the processivity of chimeric polymerases to salts depend on the structure of added HhH motifs. Regardless of the type of the construct, the thermal stability of chimeric Taq polymerases increases under the optimal ionic conditions, as compared with that of TaqDNA polymerase or its Stoffel fragment. Our approach to raise the salt tolerance, processivity, and thermostability of Taq and Pfu DNA polymerases may be applied to all pol1-and polB-type polymerases, as well as to other DNA processing enzymes. Many gene regulatory proteins contain small, discrete structural motifs that use either ␣-helices or ␤-strands for specific DNA binding. Among these are the helix-turn-helix, zinc finger, leucine zipper, and helix-loop-helix motifs (1). The motifs may arise in different molecular contexts, which is believed to occur because of either divergent evolution by means of gene duplication and insertion or structural convergence by means of the effects of selective pressures on protein function. Other proteins bind DNA by using sequence-nonspecific interactions. They belong to various protein families, such as nucleases, N-glycosylases, ligases, polymerases, and helicases that are essential for the protein-mediated synthesis and DNA repair. This compact structure with a well defined hydrophobic core mirrors the symmetry of the DNA-double helix and facilitates strong DNA binding. Protein-DNA contacts do not involve DNA bases but rather a sugar-phosphate chain, making proteins with HhH motifs able to bind DNA in the nonsequence-specific manner.A unique number of HhH motifs has been identified in DNA topoisomerase V (TopoV; refs. 6-8). The 684 C-terminal amino acids (from a total of 984 amino acids) are organized into 12 repeats of Ϸ50 amino acids long each (9). All repeats consist of two similar HhH motifs. We demonstrated earlier that Topo V proteins lacking different parts of an HhH superdomain remain fully active in relation to supercoiled DNA but become sensitive to salts (9, 10). Thus, HhH motifs play a crucial role in Topo V interactions with DNA, which a...