Simon C. Baker

Methylosulfonomonas methylovora gen. nov., sp. nov., and Marinosulfonomonas methylotropha gen. nov., sp. nov.: novel methylotrophs able to grow on methanesulfonic acid

Abstract Two novel genera of restricted facultative methylotrophs are described; both Methylosulfonomonas and Marinosulfonomonas are unique in being able to grow on methanesulfonic acid as their sole source of carbon and energy. Five identical strains of Methylosulfonomonas were isolated from diverse soil samples in England and were shown to differ in their morphology, physiology, DNA base composition, molecular genetics, and 16S rDNA sequences from the two marine strains of Marinosulfonomonas, which were isolated from British coastal waters. The marine strains were almost indistinguishable from each other and are considered to be strains of one species. Type species of each genus have been identified and named Methylosulfonomonas methylovora (strain M2) and Marinosulfonomonas methylotropha (strain PSCH4). Phylogenetic analysis using 16S rDNA sequencing places both genera in the α-Proteobacteria. Methylosulfonomonas is a discrete lineage within the α-2 subgroup and is not related closely to any other known bacterial genus. The Marinosulfonomonas strains form a monophyletic cluster in the α-3 subgroup of the Proteobacteria with Roseobacter spp. and some other partially characterized marine bacteria, but they are distinct from these at the genus level. This work shows that the isolation of bacteria with a unique biochemical character, the ability to grow on methanesulfonic acid as energy and carbon substrate, has resulted in the identification of two novel genera of methylotrophs that are unrelated to any other extant methylotroph genera.

Methanesulphonate utilization by a novel methylotrophic bacterium involves an unusual monooxygenase

Methylotroph strain M2, isolated from soil, was capable of growth on methanesulphonic acid (MSA) as sole carbon and energy source. MSA was oxidized by cell suspensions with an MSA: oxygen stoichiometry of 1.0:2.0, indicating complete conversion to carbon dioxide and sulphate. The presence of formaldehyde and formate dehydrogenases and hydroxypyruvate reductase in MSA-grown bacteria indicated the production of formaldehyde from MSA (and its further oxidation for energy generation), and assimilation of formaldehyde by means of the serine pathway. Growth yields in MSA-limited chemostat culture were a function of dilution rate, with yield ranging from 7.0 g mol-1 at D = 0.04 h-1, to 14.6 at 0.09 h-1. MSA metabolism was not initiated by hydrolysis to produce either methane or methanol, but appears to be by an NADH-dependent methanesulphonate monooxygenase, cleaving MSA into formaldehyde and sulphite. The organism lacked ribulose bisphosphate carboxylase and did not fix carbon dioxide autotrophically. It also lacked ribulose-monophosphate-dependent hexulose phosphate synthase. Growth on methanol, methylammonium and other C1 compounds was exhibited, but ability to oxidize MSA was not induced by growth on these substrates. Similarly, methylammonium (MMA) was only oxidized by strain M2 grown on MMA. Growth on methanol involved a pyrroloquinoline quinone (PQQ)-linked methanol dehydrogenase (large subunit molecular mass 60 kDa). This organism is the first methylotroph shown to have the ability to oxidize MSA, by virtue of a novel monooxygenase, and is significant in the global sulphur cycle as MSA can be a major product of the oxidation in the atmosphere of dimethyl sulphide, the principal biogeochemical sulphur gas.

Enrichment and Purification of Lipopeptide Biosurfactants

A great many methods are available for the concentration of biosurfactants from microbiological media. The strongest known biosurfactant, surfactin, serves as a model in many studies, so is used here to illustrate the diversity in approaches to product enrichment. Common physiochemical properties mean that many of these methods can be applied to other systems. Although acid precipitation is the most commonly used form of enrichment, phase separation is both an intrinsic property of surfactants and a useful tool for biotechnology. Direct liquid partitioning, membrane ultrafiltration and foam fractionation can all be regarded as phase separation technologies.

Chirality Assignment of Single‐Walled Carbon Nanotubes with Strain

Strain-induced band gap shifts that depend strongly on the chiral angle have been observed by optical spectroscopy in single-walled carbon nanotubes (SWCNTs). Uniaxial and torsional strains are generated by changing the environment surrounding the SWCNTs, using the surrounding D2O ice temperature or the hydration state of a wrapping polymer. These methods are used as diagnostic tools to determine the quantum number q and examine chiral vector indices for specific nanotubes.