Studies on the in situ physiology of Thiothrix spp. present in activated sludge

Abstract

The in situ physiology of the filamentous sulphur bacterium Thiothrix spp. was investigated in an industrial wastewater treatment plant with severe bulking problems as a result of overgrowth of Thiothrix. Identification and enumeration using fluorescence in situ hybridization (FISH) with species-specific 16S and 23S rRNA probes revealed that 5-10% of the bacteria in the activated sludge were Thiothrix spp. By using a combination of FISH and microautoradiography it was possible to study the in situ physiology of probe-defined Thiothrix filaments under different environmental conditions. The Thiothrix filaments were very versatile and showed incorporation of radiolabelled acetate and/or bicarbonate under heterotrophic, mixotrophic and chemolithoautotrophic conditions. The Thiothrix filaments were active under anaerobic conditions (with or without nitrate) in which intracellular sulphur globules were formed from thiosulphate and acetate was taken up. Thiothrix-specific substrate uptake rates and growth rates in activated sludge samples were determined under different conditions. Doubling times of 6-9 h under mixotrophic conditions and 15-30 h under autotrophic conditions were estimated. The key properties that Thiothrix might be employing to outcompete other microorganisms in activated sludge were probably related to the mixotrophic growth potential with strong stimulation of acetate uptake by thiosulphate, as well as stimulation of bicarbonate incorporation by acetate in the presence of thiosulphate.

Niche differentiation among sulfur-oxidizing bacterial populations in cave waters

“…We commonly observed the two biofilm types coexisting in a patchwork corresponding to spatial variations in water flow. All of the biofilms contained abundant elemental sulfur particles, as evidenced by microscopic observations of the particles under polarized light and by rapid dissolution of the particles in ethanol (Nielsen et al, 2000).…”

Identity, abundance and ecophysiology of filamentous bacteria belonging to the Bacteroidetes present in activated sludge plants

“…The MAR experiments were performed using 3 H-labelled and 14 C-labelled organic compounds and 14 C-labelled bicarbonate. The procedure, which includes incubation, fixation and hybridization with gene probes, addition of a radiosensitive emulsion, exposure, processing, and microscopic evaluations, is described in detail in previous papers (Andreasen & Nielsen, 1997;Lee et al, 1999;Nielsen et al, 2000). Various potential substrates were tested for uptake under aerobic conditions to determine whether gene-probe-defined representatives of Bacteroidetes were specialized or general consumers of organic substrates.…”

Filamentous bacteria existence in aerobic granular reactors

“…Wastewaters rich in reduced sulphur compounds, nutrients deficiency or in systems operated with low feeding to microorganisms (F/M) ratios are environments where Thiothrix is commonly found [7,37]. These bacteria are capable to store sulphur granules and PHA; and have rapid nutrients uptake rates under nutrient deficiency.…”