Characterization of a Small Cryptic Plasmid from Pseudomonas nitroreducens Strain TX1

Abstract

Pseudomonas nitroreducens TX1 was isolated from a rice field drainage in Taiwan. The bacterium is of special interest because of its capability to use a group of nonionic surfactants such as alkylphenol polyethoxylates even at high concentrations as a sole carbon source. In this study, a small cryptic circular plasmid, pTX1, was characterized from P. nitroreducens TX1. It is 2,286 bp in length with a GC content of 63.3% and harbors three open reading frames, ReppTX1 and functionally unidentified ORF1 and ORF2. The predicted reppTX1 gene product is homologous to Rep proteins of plasmids belonging to the pC194/pUB110 family, which is predominantly found in Gram-positive bacteria and is known to replicate by the rolling-circle mechanism. The copy number of pTX1 was estimated to be about 150 in each cell. Based on the genetic fingerprints and comparison with other plasmids, it is concluded that pTX1 replicates by a rolling circle mechanism which is rarely found for Pseudomonas plasmids.

Identification and Characterization of Novel SPHINX/BMMF-like DNA Sequences Isolated from Non-Bovine Foods

“…Only further biochemical and molecular investigations will finally answer this question. Nevertheless, several indicators point to a bacterial origin: (i) the encoded Rep proteins are closely related to Rep proteins described in plasmids or phages; (ii) the S/B group 2 sequences contain typical bacterial dso/sso motifs; (iii) several plasmids with identical structures to S/B group 2 have been described [38,[40][41][42]; (iv) the motifs (inverted repeat, ITR, DnaA-Box, oriT) identified in S/B group 1 sequences are frequently described as also occurring in plasmids [3]; and finally (v) the highly conserved nonanucleotide ori sequence [T/A]A[A/T/G]TTATAC of different Rep protein from Circoviridae, Nanoviridae, and Geminiviridae, which have been determined by Tompkins et al [4], have not been detected in the sequences described herein (for an overview see Figure 5).…”