Occurrence and diversity of plasmids in ovine isolates of Pasteurella haemolytica

Bacterial Survival Strategies in an Alkaline Tailing Site and the Physiological Mechanisms of Dominant Phylotypes As Revealed by Metagenomic Analyses

Microorganisms inhabiting mine tailings require specific metabolic strategies to survive, which may hold potential for pollution clean up. Effective in situ bioremediation will rely on an in-depth understanding of the function of the bacterial communities, especially the abundant and metabolically active phylotypes. In this study, the bacterial communities collected from an alkaline tailing site were profiled by 16S rRNA gene amplicon sequencing as well as shotgun metagenomic analysis. Our results indicated that potentials for carbon and nitrogen fixation as well as metal resistance and transformation were widespread among the bacterial community members, especially in highly enriched phylotypes, such as members of Thiobacillus and Meiothermus. Important functional microbial guilds including carbon and nitrogen fixers may contribute to phytoremediation by providing nutrients for hyperaccumulator plants. In addition, metal-metabolizing bacteria may influence metal speciation and solubility. This discovery provides an understanding for microbial survival strategies in the tailings and lays the foundation for future potential manipulation of the tailing microbiome for in situ bioremediation.

A native plasmid of Pasteurella haemolytica serotype A1: DNA sequence analysis and investigation of its potential as a vector

The complete nucleotide sequence of a 4.3 kilobase pair plasmid, pAB2, isolated from a bovine strain of Pasteurella haemolytica serotype A1, was determined. It encodes a Rob-1 type beta-lactamase and a region with homology to the mobilisation (mob) region of the Escherichia coli plasmid, ColE1. An insertion mutant of pAB2 (pTC2/81) carrying a copy of Tn5 was transferred to E coli K12 by conjugation. Subsequently pTC2/81 could be transferred by transformation to E coli HB101, but not to P haemolytica serotypes A1 or A2. However, a derivative of this construct containing only a fragment of the Tn5 insertion sequence was able to transform P haemolytica. A further construct containing a fragment of the P haemolytica A1 leucotoxin A gene, was similarly restricted to transforming E coli. These results demonstrate that the pAB2 plasmid is capable of acting as an E coli/P haemolytica shuttle vector. However, the nature of the cloned DNA sequences are important to transformation.