An unusual primary sigma factor in the Bacteroidetes phylum

Abstract

SummaryThe presence of housekeeping gene promoters with a unique consensus sequence in Bacteroides fragilis , previously described by Bayley et al.

Modes and Modulations of Antibiotic Resistance Gene Expression

“…50 nucleotides upstream from the translational start codon, of IS1224, an IS21-like element (222). In Bacteroides, the consensus sequences of the two promoter regions (Ϫ33, TTTG; Ϫ7, TANNTTTG) do not conform to those of the corresponding Ϫ35 and Ϫ10 regions recognized by typical 70 factors and do not appear to require as strict a spacing (29), a situation in keeping with the existence of a particular primary sigma factor in the Bacteroidetes phylum (259). In all high-level but not in the low-level ampicillin-resistant B. fragilis strains analyzed, a TTTG sequence was present at the cepAproximal extremity of a remnant of the IS21-like element and observed with appropriate spacing with respect to the TAcc TTTG (c, nonconsensus nucleotide) region, thus contributing to the formation of a hybrid promoter (222).…”

Mutational Analysis of theompAPromoter fromFlavobacterium johnsoniae

“…This primary sigma factor, ABfr , with some unique structural and functional characteristics, only recognized promoters from members of the phylum Bacteroidetes and thus explains the lack of functionality of E. coli promoters (55). Given that a similar sigma factor (72.1% identity) was also found in Flavobacterium johnsoniae (55), we believe that ABfr -like promoter sequences must also exist in members of the genus Flavobacterium.…”

“…This is in spite of the ubiquitous distribution of members of the phylum Bacteroidetes (6, 14, 30, 31); their importance as pathogens of fish (15, 42), birds (54), and humans (7); and their roles in transforming high-molecularweight carbon compounds in soil and aquatic environments (14). Most research on gene regulation in this phylum has targeted Bacteroides (4,11,32,49,55,57) and, to a lesser extent, Porphyromonas (27,43,57,60). Early examination of the transcriptional signals in Bacteroides fragilis indicated that its promoters exhibited features distinct from those of proteobacteria (4, 55).…”

“…Further investigation of the Bacteroides transcriptional machinery by reconstitution of homologous and heterologous RNA polymerase holoenzymes with Bacteroides, as well as E. coli, promoters allowed the identification of an unusual primary sigma factor that is confined to the phyla Bacteroidetes and Chlorobi (55). This primary sigma factor, ABfr , with some unique structural and functional characteristics, only recognized promoters from members of the phylum Bacteroidetes and thus explains the lack of functionality of E. coli promoters (55). Given that a similar sigma factor (72.1% identity) was also found in Flavobacterium johnsoniae (55), we believe that ABfr -like promoter sequences must also exist in members of the genus Flavobacterium.…”

Studies on Prevotella nuclease using a system for the controlled expression of cloned genes in P. bryantii TC1-1

“…The genetic tools that would make possible more thorough studies of prevotellas are still undeveloped despite their ecological and medical importance. This appears to be primarily due to the large phylogenetic distance between prevotellas and other well-characterized micro-organisms, and as a consequence of the rather specific genetic elements, exemplified by promoters, containing distinct 27/233 consensus sequences that are recognized by unusual primary s factor (Vingadassalom et al, 2005). Nevertheless, in two studies (Shoemaker et al, 1991;Accetto et al, 2005) the plasmid replicons and tetQ selectable marker derived from Prevotella and related colonic Bacteroides strains were used successfully for shuttle-vector introduction into the xylan-degrading ruminal species Prevotella bryantii, which forms a distinct phylogenetic lineage apparently somewhat closer to oral prevotellas than the other ruminal Prevotella species (Avguštin et al, 2001).…”