Parvibaculum lavamentivorans converts linear alkylbenzenesulphonate surfactant to sulphophenylcarboxylates, alpha,beta-unsaturated sulphophenylcarboxylates and sulphophenyldicarboxylates, which are degraded in communities.

AIMS: The aims were to test whether Parvibaculum lavamentivoransT degraded commercial linear alkylbenzenesulphonate (LAS) surfactant via omega-oxygenation and beta-oxidation to sulphophenylcarboxylates (SPCs), whether the organism was widespread and reisolable, and whether the degradative community used the 4-sulphocatechol 1,2-dioxygenase to cleave the aromatic ring from LAS. METHODS AND RESULTS: Heterotrophic P. lavamentivoransT converted LAS (side chain length C10-C13) to SPCs (C4-C13), alpha,beta-unsaturated SPCs (C4-C13) and sulphophenyldicarboxylates (SPdCs) (at least C8-C12). Identifications came from high performance liquid chromatography (HPLC) separation, an electrospray interface and mass spectrometry. No evidence for other paths was found. The degradation of LAS in trickling filters inoculated with environmental samples always showed transient SPC intermediates (HPLC) and the presence of the P. lavamentivorans morphotype in the community. One new isolate was obtained. A community able to mineralize LAS contained 4-sulphocatechol-1,2-dioxygenase at high specific activity. CONCLUSIONS: Parvibaculum lavamentivoransT degrades commercial LAS via omega-oxygenation, oxidation and chain shortening through beta-oxidation to yield a wide range of SPCs. The latter are degraded in bacterial communities which contain organisms like P. lavamentivorans, and which utilize sulphocatechol dioxygenase for ring cleavage. SIGNIFICANCE AND IMPACT OF THE STUDY: There is one widespread pathway to degrade LAS. Any traces of LAS and larger amounts of SPCs in the effluent from sewage works are exposed to degradative organisms in acclimated and pristine environments. These degradative reactions can now be studied in pure cultures.

Motility Responses and Desiccation Survival of Zoospores from the Actinomycete Kineosporia sp. Strain SR11.

During investigations into the effects of water availability on the ecology of leaf litter actinomycetes, a motile-spored strain (SR11) was isolated and identified as a Kineosporia sp. Observations of spore motility revealed they could achieve speeds up to 160 mm s?1. Chemotaxis was not observed toward several organic compounds, although K, Mg, and Ca salts of phosphate, sulfate, and halides elicited a positive response. The inability of all the corresponding Na salts, and KNO3, to act as attractants suggested that chemoattraction of SR11 spores toward inorganic compounds may be dependent on specific cations and anions. An unusual motility response to CO2 was also observed and a laminar-flow microchamber was designed and constructed to investigate this phenomenon. Increasing the CO2 concentration by as little as 0.3% (v/v) caused a rapid, synchronous arrest of spore motility. A 1% (v/v) decrease in CO2 concentration caused a similar response, although the duration of the pause was much longer. The survival responses of strain SR11 spores were observed following desiccation at various water potentials. At the highest water potential tested (-9 MPa), spore viability declined minimally during the first 24 hr but continued to decrease over 10 days. In contrast, desiccation at -87 MPa and below resulted in a 50% loss in viability within 2 hr and subsequent survival at this level of viability. Continued desiccation at -302 MPa indicated that spores were capable of long-term survival at low water potentials. Many of these responses are likely to be significant in determining the ecology of these motile-spored actinomycetes in leaf litter.

Stable-isotope probing as a tool in microbial ecology.

Microorganisms are responsible for driving the biogeochemical cycling of elements on Earth. Despite their importance and vast diversity, the taxonomic identity of the microorganisms involved in any specific process has usually been confined to that small fraction of the microbiota that has been isolated and cultivated. The recent coupling of molecular biological methods with stable-isotope abundance in biomarkers has provided a cultivation-independent means of linking the identity of bacteria with their function in the environment. Here we show that 13C-DNA, produced during the growth of metabolically distinct microbial groups on a 13C-enriched carbon source, can be resolved from 12C-DNA by density-gradient centrifugation. DNA isolated from the target group of microorganisms can be characterized taxonomically and functionally by gene probing and sequence analysis. Application of this technique to investigate methanol-utilizing microorganisms in soil demonstrated the involvement of members of two phylogenetically distinct groups of eubacteria; the alpha-proteobacterial and Acidobacterium lineages. Stable-isotope probing thus offers a powerful new technique for identifying microorganisms that are actively involved in specific metabolic processes under conditions which approach those occurring in situ.

Cultivation-independent techniques for studying methanotroph ecology.

Methane-oxidizing bacteria (methanotrophs) have attracted considerable attention over the past 30 years. They have the unique ability to use methane as sole carbon and energy source, they are found in a wide variety of environments and play a crucial role in the global methane cycle. Methanotrophs also show considerable potential for bioremediation processes such as degradation of ground water pollutants, and for production of bulk chemicals from cheap substrates. We review here the cultivation-independent molecular biological methods that are available for the detection and characterization of methanotrophs in the natural environment.