Autoaggregation of Lactobacillus reuteri is mediated by a putative DEAD-box helicase.
We have cloned and sequenced a gene from Lactobacillus reuteri that encodes a 56 kDa protein, which mediates autoaggregation of the bacteria. Using an antiserum raised against extracellular proteins from the pig intestinal isolate L. reuteri 1063, we screened a genomic lambda library derived from the same strain. Affinity purification of recombinant protein from the isolated lambda clones showed that one type of clone expressed a protein that efficiently aggregated the parental strain when added to the bacteria. Subcloning and introduction of the corresponding gene, here denoted aggHinto the L. reuteri type strain markedly enhanced aggregation. Furthermore, insertional inactivation of aggH in strain 1063 resulted in an autoaggregation-deficient phenotype. Finally, an affinity-purified and cleaved fusion of AggH protein and the maltose-binding protein, MBP, strongly promoted aggregation of L. reuteri 1063, whereas the uncleaved fusion protein was inactive. Sequencing of aggH revealed that the corresponding protein has extensive sequence homology to the large family of ATP-dependent DEAD-box helicases. These results are intriguing in view of earlier data on the promotion of genetic exchange in Lactobacillus by aggregation.
Roos
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Department of Microbiology, Swedish University of Agricultural Sciences, Box 7025, S-750 07 Uppsala, Sweden.
Lindgren
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Jonsson
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D000595:Amino Acid Sequence; D001422:Bacterial Adhesion / Q000235:genetics*; D015139:Blotting, Southern; D015153:Blotting, Western; D004591:Electrophoresis, Polyacrylamide Gel; D005798:Genes, Bacterial; D007778:Lactobacillus / Q000235:genetics* / Q000502:physiology*; D008320:Maltose / Q000378:metabolism; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D016133:Polymerase Chain Reaction / Q000379:methods; D020365:RNA Helicases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016415:Sequence Alignment
D011993:Recombinant Fusion Proteins; D008320:Maltose; D020365:RNA Helicases