Methanococci

Abstract: Plating techniques for cultivation of methanogenic bacteria have been optimized for two members of the genus Methanococcus. Methanococcus maripaludis and Methanococcus voltae were cultivated on aerobically and anaerobically prepared agar media. Maintenance of O/sub 2/ levels below 5 mu l/liter within an anaerobic glove box was necessary during plating and incubation for 90% recovery of plated cells. Under an atmosphere of H/sub 2/, CO/sub 2/, and H/sub 2/S (79:20:1), 2 to 3 days of incubation at 37 degrees C were sufficient for the formation of visible colonies. The viability of plated cells was significantly affected by the growth phase of the culture, H/sub 2/S concentration, and the volume of medium per plate. In addition, colony size of methanococci was affected by agar type, as well as by the concentrations of agar, H/sub 2/S, and bicarbonate. 12 references

Abstract: The phylum currently consists of seven classes: the Methanobacteria, the Methanococci, the Halobacteria, the Thermoplasmata, the Thermococci, the Archaeoglobi, and the Methanopyri. With the sole exception of the Methanococci, which is subdivided into three orders, each class contains a single order. The Euryarchaeota are morphologically diverse and occur as rods, cocci, irregular cocci, lancet-shaped, spiral-shaped, disk-shaped, triangular, or square cells. Cells stain Gram-positive or Gram-negative based on the presence or absence of pseudomurein in cell walls. In some classes, cell walls consist entirely of protein or may be completely absent (Thermoplasmata). Five major physiological groups have been described previously: the methanogenic Archaea, the extremely halophilic Archaea, Archaea lacking a cell wall, sulfate reducing Archaea, and the extremely thermophilic S0 metabolizers.

Abstract: In this study we found that autotrophic methanococci similar to Methanococcus maripaludis obtained up to 57% of their cellular carbon from exogenous amino acids. About 85% of the incorporation was into protein. Primarily nonpolar and basic amino acids and glycine were incorporated; only small amounts of acidic and some polar amino acids were taken up. An additional 10% of the incorporation was into the nucleic acid fraction. Because little 14CO2 was formed from the 14C-amino acids, little metabolism of the amino acids occurred. Therefore the growth stimulation by amino acids was probably due to the sparing of anabolic energy requirements. Of the amino acids incorporated, only alanine was also a sole nitrogen source for these methanococci. In contrast, Methanococcus vannielii and “Methanococcus aeolicus” are autotrophic methanococci which did not incorporate amino acids and did not utilize alanine as a sole nitrogen source. Although glutamine served as a sole nitrogen source for the autotrophic methanococci and Methanococcus voltae, a heterotrophic methanococcus, growth was due to chemical deamination in the medium. M. voltae requires leucine and isoleucine for growth. However, these amino acids were not significant nitrogen sources, and alanine was not a sole nitrogen source for the growth of M. voltae. The branched-chain amino acids were not extensively metabolized by M. voltae. Pantoyl lactone and pantoic acid were readily incorporated by M. voltae. The intact vitamin pantothenate was neither stimulatory to growth nor incorporated. In conclusion, although amino acids and vitamins are nutritionally important to both autotrophic and heterotrophic methanococci, generally they are not subject to extensive catabolism.

Abstract: 16S rDNAs amplified by PCR from 22 hyperthermophilic methanococci isolated from deep-sea hydrothermal vents were compared with those of the six type strains of the genus Methanococcus by RFLP analysis. Restriction fragments obtained with Haelll enabled four of the type species to be distinguished. Restrictions with Hhal, Bstul and Mspl were necessary to differentiate Methanococcus jannaschii and Methanococcus fervens. The results indicate that the 16S rDNA PCR-RFLP method provides a rapid and reliable tool for the identification of newly isolated hyperthermophilic Methanococcus spp.