Molecular Relationship between Two Groups of the Genus Leptospirillum and the Finding that Leptospirillum ferriphilum sp. nov. Dominates South African Commercial Biooxidation Tanks That Operate at 40°C

Abstract

Iron-oxidizing bacteria belonging to the genus Leptospirillum are of great importance in continuous-flow commercial biooxidation reactors, used for extracting metals from minerals, that operate at 40°C or less. They also form part of the microbial community responsible for the generation of acid mine drainage. More than 16 isolates of leptospirilla were included in this study, and they were clearly divisible into two major groups. Group I leptospirilla had G؉C moles percent ratios within the range 49 to 52% and had three copies of rrn genes, and based on 16S rRNA sequence data, these isolates clustered together with the Leptospirillum ferrooxidans type strain (DSM2705 or L15). Group II leptospirilla had G؉C moles percent ratios of 55 to 58% and had two copies of rrn genes, and based on 16S rRNA sequence data, they form a separate cluster. Genome DNA-DNA hybridization experiments indicated that three similarity subgroups were present among the leptospirilla tested, with two DNA-DNA hybridization similarity subgroups found within group I. The two groups could also be distinguished based on the sizes of their 16S-23S rRNA gene spacer regions. We propose that the group II leptospirilla should be recognized as a separate species with the name Leptospirillum ferriphilum sp. nov. Members of the two species can be rapidly distinguished from each other by amplification of their 16S rRNA genes and by carrying out restriction enzyme digests of the products. Several, but not all, isolates of the group II leptospirilla, but none from group I (L. ferrooxidans), were capable of growth at 45°C. All the leptospirilla isolated from commercial biooxidation tanks in South Africa were from group II.

Elevated temperature alters proteomic responses of individual organisms within a biofilm community

“…Previous culture studies have shown that while some Leptospirillum isolates are capable of growth up to 45 1C, many others are unable to grow at that temperature or higher (Coram and Rawlings, 2002;Lo, 2006;Zhang et al, 2010). Thus, it may be the case here that the colonizing Leptospirillum bacteria have a maximum growth temperature around 46 1C, thereby preventing the initial stages of biofilm formation at higher temperatures.…”

Cultivation and quantitative proteomic analyses of acidophilic microbial communities

“…Richmond Mine communities are dominated by chemoautotrophic iron-oxidizing bacteria belonging to Leptospirillum group II (Bond et al, 2000b;Tyson et al, 2004), including types related to Leptospirillum ferriphilum (Coram and Rawlings, 2002) and Leptospirillum rubarum (Goltsman et al, 2009). Leptospirillum group II typically comprises the majority of cell biomass in natural samples, and are predicted to be the key primary producers (Tyson et al, 2004).…”

Flammeovirga pacifica sp. nov., isolated from deep-sea sediment

“…T and type strains of F. yaeyamensis and F. arenaria, using the method described by Coram & Rawlings (2002) and Tønjum et al (1998). Strain WPAGA1…”