Summary auto-generated
Researchers isolated a novel Gram-negative coccus, designated strain Ben 117T, from chlorinated activated sludge collected in Western Australia using micromanipulation techniques. This bacterium exhibits morphological features consistent with 'G-bacteria,' forming characteristic tetrad clusters. The isolate is a strict aerobe, non-motile, oxidase-negative, and catalase-positive, with optimal growth between 25-30°C and pH 7.5-8.5. Notably, strain Ben 117T accumulates intracellular polyphosphate and polyhydroxybutyrate under aerobic conditions, properties suggesting potential involvement in enhanced biological phosphorus removal (EBPR) systems. Phylogenetic analysis of 16S rRNA gene sequences revealed the organism belongs to the Rhodocyclus group within β-Proteobacteria, positioned equidistantly between Ferribacterium limneticum and Dechloromonas agitata with 95% similarity. Despite phylogenetic relatedness, significant phenotypic differences (morphology, motility, oxygen requirements) distinguish this organism from related genera. The researchers propose this represents a novel genus and species: Quadricoccus australiensis gen. nov., sp. nov., representing the first cultured 'G-bacteria' member from the β-Proteobacteria. The discovery further highlights the substantial taxonomic diversity of coccoid bacteria in activated sludge ecosystems.
Key findings
- Strain Ben 117T is a novel Gram-negative coccus isolated from activated sludge belonging to the β-Proteobacteria, specifically the Rhodocyclus group, and is proposed as Quadricoccus australiensis gen. nov., sp. nov.
- The organism accumulates both polyphosphate and polyhydroxybutyrate aerobically, properties consistent with potential roles in enhanced biological phosphorus removal systems.
- Phylogenetically, strain Ben 117T is equidistantly positioned between Ferribacterium limneticum and Dechloromonas agitata (95% similarity) but differs significantly in phenotypic characteristics including morphology, motility, and aerobic lifestyle.
- The discovery represents the first cultured 'G-bacteria' representative identified in the β-Proteobacteria, expanding understanding of taxonomic diversity in activated sludge microbial communities.
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Abstract
A Gram-negative coccus, designated strain Ben 117(T), was obtained in axenic culture by micromanipulation from an Australian activated sludge biomass sample, which had been subjected to chlorination in order to alleviate problems associated with foaming and bulking. This isolate was a strict aerobe and grew in axenic culture, also appearing in biomass samples as cocci or clusters of cocci in tetrads, thus resembling the morphotype 'G-bacteria' seen commonly in activated sludge samples. Strain Ben 117(T) was non-motile, aerobic, oxidase-negative and catalase-positive and grew between 15 and 30 degrees C, with an optimum of 25--30 degrees C. The pH range for growth was between 6.0 and 8.5, with an optimum of 7.5--8.5. The isolate stained positively for intracellular polyphosphate and poly-beta-hydroxybutyrate and its G+C content was 67 mol%. 16S rDNA sequence analysis suggests that strain Ben 117(T) is phylogenetically different from members of the genera Amaricoccus, Gram-negative 'G-bacteria' isolated previously in this laboratory. Ben 117(T) is a member of the Rhodocyclus group in the beta-Proteobacteria and equidistantly placed (similarity value of 95%) between Ferribacterium limneticum and Dechloromonas agitata (mean similarity value of 92% with the genus Rhodocyclus). Based on phenotypic and phylogenetic evidence, it is proposed that strain Ben 117(T) be designated a novel species in a new genus, Quadricoccus australiensis gen. nov., sp. nov.; the type strain is Ben 117(T) (=NCIMB 13738(T)=CIP 107055(T)).