Colorless Sulfur Bacteria Research Articles

Competition between anoxygenic phototrophic bacteria and colorless sulfur bacteria in a microbial mat

The populations of chemolithoautotrophic (colorless) sulfur bacteria and anoxygenic phototrophic bacteria were enumerated in a marine microbial mat. The highest population densities were found in the 0–5 mm layer of the mat: 2.0 × 10 9 cells cm −3 sediment, and 4.0 × 10 7 cells cm −3 sediment for the colorless sulfur bacteria and phototrophs, respectively. Kinetic parameters for thiosulfate-limited growth were assessed for Thiobacillus thioparus T5 and Thiocapsa roseopersicina M1, both isolated from microbial mats. For Thiobacillus T5, growing at a constant oxygen concentration of 43 μmol l −1, μ max was 0.336 h −1 and K s 0.8 μmol l −1. Phototrophically grown Thiocapsa strain M1 displayed a μ max of 0.080 h −1 and a K s of 8 μmol l −1 when anoxically grown under thiosulfate limitation. In a competition experiment with thiosulfate as electron donor, Thiocapsa became dominant during a 10-h oxic/14-h anoxic regimen at continuous illumination, despite the higher affinity for thiosulfate of Thiobacillus.

Ratio of biological and chemical oxidation during the aerobic elimination of sulphide by colourless sulphur bacteria

Culture conditions were evaluated for their relevance to chemical and biological oxidation of sulphide in aqueous solution. With a mixed culture of colourless sulphur bacteria sulphide oxidation was investigated over a concentration range of 0.005 to 3.5 mm S2−, a pH range from 1.0 to 9.0 and temperatures from 10 to 40° C. Biological sulphide oxidation quickly decreased when fermentation conditions were suboptimal and the proportion of chemical oxidation increased with high pH values and sulphide concentration and increasing temperature. The optimal conditions for biological activity were found to be 3 mm S2−, pH 7.0, and a mesophilic temperature (40° C).

Biotechnological Sulphide Removal from Effluents

A new system for sulphide removal is reported in which sulphide is converted to elemental sulphur using colourless sulphur bacteria. A 4 m3 biorotor reactor has been tested using sulphide-containing anaerobically treated papermill wastewater. Sulphide removal efficiencies well above 90% were achieved at a hydraulic retention time of 19 minutes, using Pall rings of 2.5 cm or Bio-Net 200 as carrier materials. It was also found that reticulated polyurethane is not suitable as carrier material for the sulphide removal process in the presence of fatty acids.

Methylated sulfur compounds in microbial mats: in situ concentrations and metabolism by a colorless sulfur bacterium

The concentrations of the volatile organic sulfur compounds methanethiol, dimethyl disulfide, and dimethyl sulfide (DMS) and the viable population capable of DMS utilization in laminated microbial ecosystems were evaluated. Significant levels of DMS and dimethyl disulfide (maximum concentrations of 220 and 24 nmol cm3 of sediment-1, respectively) could be detected only at the top 20 mm of the microbial mat, whereas methanethiol was found only at depth horizons from 20 to 50 mm (maximum concentration of 42 nmol cm3 of sediment-1). DMS concentrations in the surface layer doubled after cold hydrolysis of its precursor, dimethylsulfoniopropionate. Most-probable-number counts revealed 2.2 x 10(5) cells cm3 of sediment-1, in the 0- to 5-mm depth horizon, capable of growth on DMS as the sole source of energy. An obligately chemolithoautotrophic bacillus designated strain T5 was isolated from the top layer of the marine sediment. Continuous culture studies in which DMS was the growth-limiting substrate revealed a maximum specific growth rate of 0.10 h-1 and a saturation constant of 90 mumol liter-1 for aerobic growth on this substrate.

Study of the "sulfur-turf": a community of colorless sulfur bacteria growing in hot spring effluent.

Sulfur-turf is one of the so-called “sulfureta” which are massive aggregates of colorless sulfur bacteria. Interest in the ecological and physiological aspects of the sulfuretum has strongly increased not only due to the discovery of massive occurrence of colorless sulfur bacteria in an area of hydrothermal vents but also due to the possibility of its significant contribution to the sulfur cycle in the coastal region. Here, I review the types, habitats, and bacterial constituents of the sulfur-turf, and further, reveal the microaerophilic oxidation of elemental sulfur by the sulfur-turf and discuss the possibility of the detoxification of hydrogen sulfide with peroxides. The habitat of the sulfur-turf is regarded as a thermostating, continuous culture enriched with hydrogen sulfide. The massive aggregates including the sulfur-turf are very useful, because they can be harvested directly from their habitats without the need for isolation and mass cultivation. Taking advantage of these massive aggregates, we should design experiments in situ and also in the laboratory to clarify the ecology and physiology of the colorless sulfur bacteria. It is necessary to elucidate the microenvironment caused by bacterial aggregation using microelectrodes, but, on the other hand, more interest should be focused on the bacterial reaction to environmental factors, especially oxygen tension.

Swept Away: Resuspension of Bacterial Mats Regulates Benthic-Pelagic Exchange of Sulfur

Filaments and extracellular material from colorless sulfur bacteria (Beggiatoa spp.) form extensive white sulfur mats on surface sediments of coastal, oceanic, and even deep-sea environments. These chemoautotrophic bacteria oxidize soluble reduced sulfur compounds and deposit elemental sulfur, enriching the sulfur content of surface sediment fivefold over that of deeper sediments. Laboratory flume experiments with Beggiatoa mats from an intertidal sandflat (Nova Scotia) demonstrated that even slight erosion of sediment causes a flux of 160 millimoles of sulfur per square meter per hour, two orders of magnitude greater than the flux produced by sulfur transformations involving either sulfate reduction or sulfide oxidation by benthic bacteria. These experiments indicate that resuspension of sulfur bacterial mats by waves and currents is a rapid mechanism by which sediment sulfur is recycled to the water column. Benthic communities thus lose an important storage intermediate for reduced sulfur as well as a high-quality bacterial food source for benthic grazers.

Chemolithotrophic growth of the phototrophic sulfur bacteriumThiocapsa roseopersicina

Abstract Chemotrophic growth capacities of the purple sulfur bacterium Thiocapsa roseopersicina strain M1 were studied in continuous culture under thiosulfate limitation. Pigment synthesis was completely inhibited upon a shift from anaerobic to semi-aerobic conditions (52 μM O 2 ) in the light, but no active breakdown occurred. During the transient state, the cells grew in a mixed photo- and chemolithotrophic mode; the specific respiration rate gradually increased with a concomitant drop in the bacteriochlorophyll a content. Photolithotrophically grown cells have the ability to respire. It was concluded that photosynthesis and respiration compete for electrons, but that photosynthesis is preferred under electron donor-limiting conditions, when the cells still contain large amounts of pigments. Eventually, a fully chemolithotrophic steady state was attained. The chemolithotropic growth of T. roseopersicina was studied in the dark under semiaerobic conditions at various dilution rates. The maximum specific growth rate was 68% of the maximum attainable growth rate under photolithotrophic conditions. The growth affinity for thiosulfate was high ( K m = 1.5 μ M). The yield on thiosulfate under chemolithotrophic conditions exceeded that of thiobacilli. Oxygen uptake was studied in short-term experiments. It was shown that respiration in T. roseopersicina has a K m of approx. 1 μM O 2 . the ecological importance for T. roseopersicina of chemolithotrophic growth and pigment content is discussed with respect to the occurrence of T. roseopersicina in laminated microbial ecosystems and its possible competition with colorless sulfur bacteria.

Competition for sulfide among colorless and purple sulfur bacteria in cyanobacterial mats

The vertical zonation of light, O 2, H 2S, pH, and sulfur bacteria was studied in two benthic cyanobacterial mats from hypersaline ponds at Guerrero Negro, baja California, Mexico. The physical-chemical gradients were analyzed in the upper few mm at ⩽ 100 μm spatial resolution by microelectrodes and by a fiber optic microprobe. In mats, where oxygen produced by photosynthesis diffused far below the depth of the photic zone, colorless sulfur bacteria ( Beggiatoa sp.) were the dominant sulfide oxidizing organisms. In a mat, where the O 2H 2S interface was close to the photic zone, but yet received no significant visible light, purple sulfur bacteria ( Chromatium sp.) were the dominant sulfide oxidizers. Analysis of the spectral light distribution heare showed that the penetration of only 1% of the incident near-IR light (800–900 nm) into the sulfide zone was sufficient for the development of Chromatium in a narrow band of 300 μm thickness. The balance betweem O 2 and light penetration down into the sulfide zone thus deterined in mcro-scale which type of sulfur bacteria becamed dominant.

Colorless Sulfur Bacteria, Beggiatoa spp. and Thiovulum spp., in O 2 and H 2 S Microgradients

The interactions between colorless sulfur bacteria and the chemical microgradients at the oxygen-sulfide interface were studied in Beggiatoa mats from marine sediments and in Thiovulum veils developing above the sediments. The gradients of O(2), H(2)S, and pH were measured by microelectrodes at depth increments of 50 mum. An unstirred boundary layer in the water surrounding the mats and veils prevented microturbulent or convective mixing of O(2) and H(2)S. The two substrates reached the bacteria only by molecular diffusion through the boundary layer. The bacteria lived as microaerophiles or anaerobes even under stirred, oxic water. Oxygen and sulfide zones overlapped by 50 mum in the bacterial layers. Both compounds had concentrations in the range of 0 to 10 mumol liter and residence times of 0.1 to 0.6 s in the overlapping zone. The sulfide oxidation was purely biological. Diffusion calculations showed that formation of mats on solid substrates or of veils in the water represented optimal strategies for the bacteria to achieve a stable microenvironment, a high substrate supply, and an efficient competition with chemical sulfide oxidation. The continuous gliding movement of Beggiatoa cells in mats or the flickering motion of Thiovulum cells in veils were important for the availability of both O(2) and H(2)S for the individual bacteria.

Ecology of the bacteria of the sulphur cycle with special reference to anoxic-oxic interface environments.

H2S is produced as a main end-product of anaerobic mineralization in anoxic, sulphate-rich environments by a diverse population of sulphate-reducing bacteria. The sulphate reducers can carry out an almost complete oxidation of detrital organic matter to CO2. The H2S consequently becomes an important electron carrier from the anoxic to the oxic world. Thiobacilli and other colourless sulphur bacteria have the potential to oxidize the H2S at the oxic-anoxic interface in sediments or stratified waters, but their role is still poorly understood. A comparison of sulphide oxidation processes in the chemoclines of the Black Sea, the Solar Lake and in A beggiatoa mat indicated that depth scales and retention times of coexisting O2 and H2S regulate the bacterial involvement in the sulphide oxidation. The H2S specialists, Beggiatoa and Thiovulum, are optimally adapted to compete with the autocatalytic oxidation of H2S by O2. Microelectrode measurements show retention times of O2-H2S in the bacterial mats or veils of less than 1 s. In photic chemoclines of stratified waters or sulfureta, the phototrophic sulphur bacteria or cyanobacteria interact with the sulphide oxidation at the O2-H2S interface. Short cycles between H2S and intermediate oxidation products, So or S2O2 3-, are created. The bacteria of the sulfuretum are highly adapted to the diurnal rhythm of light, O2 and H2S.

Competition for inorganic substrates among chemoorganotrophic and chemolithotrophic bacteria

In aerobic enrichment experiments with a chemostat, using phosphate-limited lactate medium, aSpirillum sp. predominated at the lower range of dilution rates. At the higher dilution rates an (chemoorganotrophic) unidentified rod-shaped bacterium came to the fore. The same result was obtained in competition experiments with pure cultures of the two bacteria. Growth parameters were: Rod,Μ max=0.48 hr(-1),k s(PO4 (3-))=6.6×10(-N) M;Spirillum, Μ max=0.24 hr(-1)· ks(PO4 (3-)) =2.7×10(-8) M. TheSpirillum grew faster than the rod at low dilution rates, not only under phosphate-limitation but also in K(+)-,Mg(2+)-, NH4 (+)-, aspartate-, succinate-, and lactate-limited cultures. Both organisms showed little substrate specificity and could utilize a similar range of carbon and energy sources. The results support the view that part of the diversity among bacteria in the natural environment is based on selection toward substrate concentration. Another set of competition experiments was carried out with pure cultures of two marine obligately chemolithotrophic colorless sulfur bacteria,Thiobacillus thioparus andThiomicrospira pelophila. Tms. pelophila outgrewT. thioparus at low dilution rates under iron limitation, while the reverse was true at high dilution rates. It is concluded that the relatively fast growth ofTms. pelophila at low iron concentration may explain its higher sulfide tolerance. Organisms showing a selection advantage at very low concentrations of limiting substrates appear to have a relatively high surface to volume ratio.

Distribution of colorless sulfur bacteria (Beggiatoa spp.) in a coastal marine sediment

The populations of Beggiatoa species were quantified in the sediments of a brackish fjord (Limfjorden, Denmark) over a period of 1 year. The bacterial distribution was compared to the physical structure of the sediment, the redox profile, the concentration and production rate of H2S, and the rate of O2 consumption. The bacteria are absent in fine and in medium-grained sand, but in muds which are aggregated in faecal pellets very high population densities are found throughout the year with average biomasses of 5 to 20 g m-2. The bacteria seldom form coatings on the surface, but are distributed within the upper few centimeters of oxic sediment. They receive H2S partly from the lower anoxic layers and partly from reduced microniches scattered in the oxidized zone. Estimates of their metabolic rates indicate that Beggiatoa spp. may play a significant role in the sulfur and carbon cycles of the investigated sediments.

The habitat and description of a new genus of sulphur bacterium.

SUMMARY A new species and genus of colourless sulphur bacteria, for which the name Thiodendron mucosum is proposed, is described from two habitats in Florida. Its morphology and physiology relate it to the Beggiatoaceae, but it is branching, non-filamentous and non-motile so it should not be included in that family and a new family should be created for it. Some characteristics of its environment are discussed and also the organisms common to such an environment. It is probable that the particular organisms are closely connected to the metabolism of sulphur, while their variety and biomass attribute an important role to sulphur in nature, especially in environments containing little or no oxygen.