A Methane-Dependent Coccus, with Notes on Classification and Nomenclature of Obligate, Methane-Utilizing Bacteria

Abstract

FosTER, J. W. (The University of Texas, Austin), AND RICHARD H. DAVIS. A methane-dependent coccus, with notes on classification and nomenclature of obligate, methane-utilizing bacteria. J. Bacteriol. 91:1924-1931. 1966.-A new coccusshaped bacterium capable of aerobic growth at the expense of methane or methanol in a mineral salts medium is described. The organism did not grow at the expense of any of the conventional substrates or homologous hydrocarbons tested. It is gram-negative, nonmotile, and thermotolerant. It grows well at 50 C, optimally at 37 C, but does not grow at 55 C. The cells are encapsulated and have a characteristic diplococcoid arrangement. Washed, "resting-cell" suspensions oxidized certain primary alcohols and short-chain alkanes, an example of "nongrowth oxidation." Of the methane-C utilized, 86% was "fixed" in organic form; the remainder was oxidized to CO2. The guanine-cytosine content of the extracted deoxyribonucleic acid was 62.5%. Obligate methane-utilizing bacteria are considered as "one-carbon" organisms rather than hydrocarbon utilizers. The assimilation pathway in the obligate methane-methanol bacteria is different from that in the facultative methanol utilizers. Nomenclatural problems arising from the use of the prefix "Methano-" to denote both bacteria that oxidize methane and bacteria that produce methane are discussed. The obligate, one-carbon, methane-methanol bacteria are considered as "methyl" utilizers, and the prefix "Methylo-" is suggested as a solution to the problem of generic cognomens. "Methylococcus capsulatus" gen. n., sp. n. is the name proposed for the new methane coccus.

Fine Structure of Methane‐utilizing Bacteria

“…The former have thc appearance of lipid inclusions and the latter resemble poly-P-hydroxybutyrate granules (Stevenson & Socolofsky, 1966;Ellar, Lundgren & Slepecky, 1967). Neither Foster & Davis (1966) nor we have detected poly-p-hydroxybutyrate in M . capsulatus although it has been demonstrated in all of our isolates of methane-utilizing bacteria, by the method of Law & Slepecky (1961).…”

“…capmdatu-s are probably capsular material. Such material is not usually preserved in electron microscope preparations ; however, this particular polysaccharide is somewhat unusual since it can only be dissolved in water by boiling (Foster & Davis, 1966). It may be retained, therefore, around the cells during electron microscopy.…”

Response to mercury (II) ions in Methylococcus capsulatus (Bath)

“…Methylococcus capsulatus is a methanotrophic member of the Gammaproteobacteria first isolated from sewage sludge (Foster & Davis, ). Whilst the type strain (Texas T ) is poorly characterized, the ‘Bath’ strain (Whittenbury et al ., ) is the archetypal model methanotrophic bacterium.…”

Production, modification, and consumption of atmospheric trace gases by microorganisms

“…Methane is utilized as a growth substrate mainly by bacteria and only under aerobic conditions. I n addition to some methane oxidizing bacteria known since a long time like Pseudomonas methanica (Sohngen, 1906;Dworkin & Foster, 1956;Leadbetter & Foster, 1960) or Methylococcus capsulatus (Foster & Davis, 1966) over a 100 methane utilizing bacteria were isolated recently (Whittenbury, 1969;Whittenbury et al, 1970). Most of the methane oxidizing bacteria are obligately bound to this substrate; they use neither long chain hydrocarbons nor are able to grow on the conventional substrates.…”