Summary auto-generated
Researchers isolated and characterized a novel anaerobic bacterium, designated strain KRE 4T, from sewage sludge that uniquely degrades creatinine as its sole carbon and energy source. This Gram-positive, non-spore-forming, rod-shaped organism completely metabolizes creatinine via creatine, sarcosine, and glycine to produce acetate, monomethylamine, ammonia, and carbon dioxide. Growth requires selenium and is stimulated by formate or hydrogen as electron donors. Cell-free extracts demonstrated the involvement of creatine reductase, sarcosine reductase, and glycine reductase enzymes. Phylogenetic analysis using 16S rRNA gene sequencing revealed the organism belongs to the genus Tissierella, showing highest sequence similarity (approximately 95%) with other Tissierella species. Based on distinct phenotypic characteristics, restricted substrate specificity, and phylogenetic distinctiveness compared to existing Tissierella species, the bacterium was classified as a new species: Tissierella creatinophila sp. nov., with type strain KRE 4 (DSM 6911T). The strain's limited metabolic substrate range distinguishes it from the related species T. creatinini and T. praeacuta.
Key findings
- A novel strictly anaerobic bacterium, Tissierella creatinophila sp. nov., was isolated from sewage sludge and uniquely uses creatinine as its sole source of carbon and energy.
- The organism degrades creatinine through a selenium-dependent pathway involving creatine reductase, sarcosine reductase, and glycine reductase, with formate or hydrogen serving as electron donors.
- Phylogenetic analysis based on 16S rRNA gene sequencing placed the organism in the genus Tissierella with approximately 95% sequence similarity to existing Tissierella species.
- Unlike the closely related T. creatinini, strain KRE 4T cannot utilize intermediate metabolites (sarcosine, glycine, N-methylhydantoin) as sole substrates for growth, demonstrating a restricted metabolic spectrum.
- The bacterium produces acetate, monomethylamine, and ammonia as final fermentation products from creatinine degradation.
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Abstract
A strictly anaerobic, Gram-positive, non-spore-forming bacterium was isolated from sewage sludge which grew on creatinine as sole source of carbon and energy. This new isolate, designated strain KRE 4T, totally degraded creatinine via creatine, sarcosine and glycine to the products acetate, monomethylamine, ammonia and carbon dioxide. Growth on creatinine or creatine was selenium-dependent and stimulated by formate, indicating the involvement of a creatine reductase, sarcosine reductase and/or glycine reductase. This was substantiated by the fact that creatine, sarcosine and glycine were reduced by cell-free extracts. Growth on creatinine or creatine was also possible in the absence of formate, but with an increase in doubling time. The new bacterium occurred as rod-shaped cells, which exhibited an angular form (2-6 microns long and 0.7-1.1 microns wide) and showed motility by means of peritrichous flagella. The G+C content of the DNA was 30 mol %. Comparative 16S rRNA sequence analysis demonstrated that strain KRE 4T represents a new subline within the genus Tissierella. Due to its very restricted substrate spectrum and the inability of whole cells to utilize sarcosine and glycine as intermediates of creatine breakdown, this organism can be readily separated from currently described species of Tissierella. Therefore, based on the phenotypic and phylogenetic distinctiveness of the new isolate, it si proposed that the bacterium be classified as a new species of the genus Tissierella, Tissierella creatinophila sp. nov. The type strain is KRE 4 (= DSM 6911T).