Revisiting the pink-red pigmented basidiomycete mirror yeast of the phyllosphere

© The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in MicrobiologyOpen 5 (2016): 846–855, doi:10.1002/mbo3.374.By taking advantage of the ballistoconidium-forming capabilities of members of the genus Sporobolomyces, we recovered ten isolates from deciduous tree leaves collected from Vermont and Washington, USA. Analysis of the small subunit ribosomal RNA gene and the D1/D2 domain of the large subunit ribosomal RNA gene indicate that all isolates are closely related. Further analysis of their physiological attributes shows that all were similarly pigmented yeasts capable of growth under aerobic and microaerophilic conditions, all were tolerant of repeated freezing and thawing, minimally tolerant to elevated temperature and desiccation, and capable of growth in liquid or on solid media containing pectin or galacturonic acid. The scientific literature on ballistoconidium-forming yeasts indicates that they are a polyphyletic group. Isolates of Sporobolomyces from two geographically separated sites show almost identical phenotypic and physiological characteristics and a monophyly with a broad group of differently named Sporobolomyces/Sporidiobolus species based on both small subunit ribosomal RNA (SSU rRNA) and D1/D2 domains of the LSU rRNA gene sequences

Structured Multiple Endosymbiosis of Bacteria and Archaea in a Ciliate from Marine Sulfidic Sediments: A Survival Mechanism in Low Oxygen, Sulfidic Sediments?

Marine micro-oxic to sulfidic environments are sites of intensive biogeochemical cycling and elemental sequestration, where prokaryotes are major driving forces mediating carbon, nitrogen, sulfur, phosphorus, and metal cycles, important from both biogeochemical and evolutionary perspectives. Associations between single-celled eukaryotes and bacteria and/or archaea are common in such habitats. Here we describe a ciliate common in the micro-oxic to anoxic, typically sulfidic, sediments of Santa Barbara Basin (CA, USA). The ciliate is 95% similar to Parduzcia orbis (18S rRNA). Transmission electron micrographs reveal clusters of at least three different endobiont types organized within membrane-bound sub-cellular regions. Catalyzed reporter deposition–fluorescent in situ hybridization and 16S rRNA clone libraries confirm the symbionts include up to two sulfate reducers (Desulfobulbaceae, Desulfobacteraceae), a methanogen (Methanobacteriales), and possibly a Bacteroidete (Cytophaga) and a Type I methanotroph, suggesting synergistic metabolisms in this environment. This case study is discussed in terms of implications to biogeochemistry, and benthic ecology

Metabolism of sulfonic acids and other organosulfur compounds by sulfate-reducing bacteria

This article presents a short review of recent research that established the ability of sulfate‐reducing bacteria to utilize sulfonic acids as terminal electron acceptors (TEA) for anaerobic respiratory growth. Newer studies of the bacterium most intensively investigated, Desulfovibrio desulfuricans, strain ICI, are also reported. When either of two sulfonic acids examined—isethionate (2‐hydroxyethanesulfonate) or cysteate (alanine‐3‐sulfonate)—served as sole TEA, key changes in the cells’ enzymo‐logical profile occurred: decreased production of two enzymes involved in sulfate reduction, namely, ATP sulfurylase and APS reductase. Similar reduction in content of these enzymes was seen when either sulfite or fumarate served as TEA. Protein profiles (polyacrylamide gel electrophoresis) of extracts of cells grown with different TEA revealed the presence of a 97‐kD polypeptide apparently unique to isethionate‐grown cells; a different polypeptide was noted in extracts of cysteate‐grown cells. The absence of such stained bands in extracts of sulfate‐grown cells suggests that these polypeptides are involved in utilization of sulfonic acids as TEA. H2 threshold values of cells growth with isethionate as TEA were significantly lower than for cells growing with sulfate or sulfite, suggesting that energy may be conserved in the cleavage of isethionate's C‐S linkage. A survey of the distribution of sulfonic acids in diverse habitats combined with the ability of other anaerobic bacteria to respire these compounds leads to the suggestion sulfonate reduction is likely to be significant in the sulfur cycle

Sulfonates: novel electron acceptors in anaerobic respiration

The enrichment and isolation in pure culture of a bacterium, identified as a strain of Desulfovibrio, able to release and reduce the sulfur of isethionate (2-hydroxyethanesulfonate) and other sulfonates to support anaerobic respiratory growth, is described. The sulfonate moiety was the source of sulfur that served as the terminal electron acceptor, while the carbon skeleton of isethionate functioned as an accessory electron donor for the reduction of sulfite. Cysteate (alanine-3-sulfonate) and sulfoacetaldehyde (acetaldehyde-2-sulfonate) could also be used for anaerobic respiration, but many other sulfonates could not. A survey of known sulfate-reducing bacteria revealed that some, but not all, strains tested could utilize the sulfur of some sulfonates as terminal electron acceptor. Isethionate-grown cells of Desulfovibrio strain IC1 reduced sulfonate-sulfur in preference to that of sulfate; however, sulfate-grown cells reduced sulfate-sulfur in preference to that of sulfonate

Low-molecular-weight sulfonates, a major substrate for sulfate reducers in marine microbial mats:

Several low-molecular-weight sulfonates were added to microbial mat slurries to investigate their effects on sulfate reduction. Instantaneous production of sulfide occurred after taurine and cysteate were added to all of the microbial mats tested. The rates of production in the presence of taurine and cysteate were 35 and 24 M HS ؊ h ؊1 in a stromatolite mat, 38 and 36 M HS ؊ h ؊1 in a salt pond mat, and 27 and 18 M HS ؊ h ؊1 in a salt marsh mat, respectively. The traditionally used substrates lactate and acetate stimulated the rate of sulfide production 3 to 10 times more than taurine and cysteate stimulated the rate of sulfide production in all mats, but when ethanol, glycolate, and glutamate were added to stromatolite mat slurries, the resulting increases were similar to the increases observed with taurine and cysteate. Isethionate, sulfosuccinate, and sulfobenzoate were tested only with the stromatolite mat slurry, and these compounds had much smaller effects on sulfide production. Addition of molybdate resulted in a greater inhibitory effect on acetate and lactate utilization than on sulfonate use, suggesting that different metabolic pathways were involved. In all of the mats tested taurine and cysteate were present in the pore water at nanomolar to micromolar concentrations. An enrichment culture from the stromatolite mat was obtained on cysteate in a medium lacking sulfate and incubated anaerobically. The rate of cysteate consumption by this enrichment culture was 1.6 pmol cell ؊1 h ؊1 . Compared to the results of slurry studies, this rate suggests that organisms with properties similar to the properties of this enrichment culture are a major constituent of the sulfidogenic population. In addition, taurine was consumed at some of highest dilutions obtained from most-probable-number enrichment cultures obtained from stromatolite samples. Based on our comparison of the sulfide production rates found in various mats, low-molecular-weight sulfonates are important sources of C and S in these ecosystems. The sulfur cycle plays an important role in the geomicrobiology of intertidal and coastal sediments The sulfonates are a group of organosulfur compounds that are commonly found in household and industrial wastewater. Linear alkyl sulfonates are major constituents of detergents (58), and the catabolism of these compounds has been well documented (6, 18) and includes carbon-sulfur bond breakage pathways (39, 44). Recently, it has been shown that a range of low-molecular-weight sulfonates are present in the marine environment. A variety of different marine sediments contain significant amounts of sulfonates, which comprise 20 to 40% of the organosulfur pool (65). Unfortunately, the composition of the sulfonate pool was not characterized further in the study of Vairavamurthy et al. (65). However, several sources of sulfonates have been identified in the marine environment. Sulfonates can be the sole source of sulfur or nitrogen for marine phytoplankton (7), and sulfolipids can be major biomembrane constituents in microscopic algae (56, 57), cyanobacteria (2, 26), diatoms (1), and bacteria (24). Sulfonate-containing exopolymers may be present in benthic diatoms and support the gliding motility of these organisms, like suggestions made for bacteria (25). Taurine (2-aminoethanesulfonate) is present in marine diatoms (34) and zooplankton (9), presumably as a major osmolyte. The intracellular concentration of these compounds typically exceeds 0.2 M, which could easily explain the occurrence of sulfonates in the estuarine environment. Similarly, cysteate (alanine 3-sulfonate) is one of the oxidation products of cysteine residues in proteins (55, 60), and isethionate (2-hydroxyethanesulfonate) has been found in marine algae (31). Clearly, many different sources contribute to the pool of low-molecular-weight sulfonates in the marine environment. Taurine is one of the several amino acids that are readily bioavailable in marine sediments (48). In addition to being used for anabolic purposes, amino acids are catabolized by microbes. Under anoxic conditions, this occurs through fermentation and, more importantly, sulfate reduction (8, 51, 61). The nitrogen-containing sulfonates taurine and cysteate can also be utilized by sulfate-reducing bacteria (SRB) Microbial mats, including microbial mats associated with sal