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Category: Microbial Genetics and Molecular Biology; Bacterial Pathogenesis
Type 4 Pili in the Families Moraxellaceae and Neisseraceae, Page 1 of 2
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This chapter reviews studies on type 4 pili from the species Moraxella bovis, Moraxella lacunata, and Moraxella nonliquefaciens of the family Moraxellaceae and Eikenella corrodens, Kingella denitrificans, and Kingella kingae of the family Neisseriaceae. K. kingae was originally classified as Moraxella kingii and was then transferred to the new genus Kingella within the family Neisseriaceae in 1976. Further studies with M. nonliquefaciens, M. bovis, and M. kingii confirmed the association between the "spreading-corroding" (SC) colony type and piliation. Researchers studied thin sections of M. bovisin the electron microscope and concluded that the pili were distributed peritrichously around the cell. When M. bovis Epp63 was propagated on 5% sheep blood agar, one N-type and six distinct piliated colony types were observed. Thus, pellicle formation can be used as an enrichment procedure to isolate the often rare variants switching from the nonpiliated to the piliated state. The competence for DNA transformation in piliated E. corrodens has also been demonstrated. Further studies on the function and genetics of type 4 pili may lead to a better understanding of the roles that they play in so many bacterial species.
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SC and N colony types of M. bovis on bovine blood agar (A) or GC agar medium (B). (A) The SC colonies exhibit a “fried egg” appearance, while the N colony is relatively featureless. (B) The SC colonies are small and domed, while the N colony is much larger.
SC and N colony types of M. bovis on bovine blood agar (A) or GC agar medium (B). (A) The SC colonies exhibit a “fried egg” appearance, while the N colony is relatively featureless. (B) The SC colonies are small and domed, while the N colony is much larger.
(A) Diagram of the M. bovis pilin gene inversion region in orientation 1, with tfpQ in the expression locus. Parentheses represent the sites of inversion, and lines beneath the map show the direction of transcription (dashed lines indicate genes for which we have no evidence of transcription). (B) The same region in orientation 2, with tfpI in the expression locus.
(A) Diagram of the M. bovis pilin gene inversion region in orientation 1, with tfpQ in the expression locus. Parentheses represent the sites of inversion, and lines beneath the map show the direction of transcription (dashed lines indicate genes for which we have no evidence of transcription). (B) The same region in orientation 2, with tfpI in the expression locus.
Comparison of the pilin gene inversion regions of M. bovis and M. lacunata. The hatched region of tfpB represents the portion of the gene present in M. bovis but absent from M. lacunata.
Comparison of the pilin gene inversion regions of M. bovis and M. lacunata. The hatched region of tfpB represents the portion of the gene present in M. bovis but absent from M. lacunata.
(A) Diagram of the arrangement of two pilin genes and a hemagglutinin gene from the E. corrodens type strain ATCC 23834. (B) Similar genes from E. corrodens 31745. The region past ecpD does not contain a gene equivalent to the hemagglutinin gene found in the type strain. The arrows below the genes show the directions of transcription.
(A) Diagram of the arrangement of two pilin genes and a hemagglutinin gene from the E. corrodens type strain ATCC 23834. (B) Similar genes from E. corrodens 31745. The region past ecpD does not contain a gene equivalent to the hemagglutinin gene found in the type strain. The arrows below the genes show the directions of transcription.