SUMMARYSaccharomyces cerevisiae accumulated Co2+ and Cdz+ by two processes : the first, which was metabolism-independent, was presumably cation binding to the cell surface; this was followed by metabolism-dependent, progressive uptake of relatively large amounts of the cations. Two K+ ions were released for each Co2+ ion taken up in freshly prepared cell suspensions whereas extensive loss of cellK+ followed the uptake of Cd2+. Co2+ and Cda+ appeared to be accumulated via a general cation uptake system, with limited specificity related to the ionic radii of the cations.

Aims: To develop a method to detect bacteria from environmental samples that are able to metabolize lignin. Methods and Results: A previously developed UV-vis assay method for lignin degradation activity has been developed for use as a spray assay on agar plates. Nine mesophilic strains were isolated using this method from woodland soil incubated in enrichment cultures containing wheat straw lignocellulose: four Microbacterium isolates, two Micrococcus isolates, Rhodococcus erythropolis (all Actinobacteria) and two Ochrobactrum isolates (Alphaproteobacteria). Three thermotolerant isolates were isolated from the same screening method applied at 45°C to samples of composted wheat straw from solid-state fermentation: Thermobifida fusca and two isolates related to uncharacterized species of Rhizobiales and Sphingobacterium (Bacteroidetes), the latter strain showing tenfold higher lignin degradation activity than other isolates. The isolated strains were able to depolymerize samples of size-fractionated high molecular weight and low molecular weight Kraft lignin, and produced low molecular weight metabolites oxalic acid and protocatechuic acid from incubations containing wheat straw lignocellulose. Conclusions: A new method for the isolation of bacteria able to metabolize lignin has been developed, which has been used to identify 12 bacterial isolates from environmental sources. The majority of isolates cluster into the Actinobacteria and the Alphaproteobacteria. Significance and Impact of the Study: Lignin-degrading bacterial strains could be used to convert lignin-containing feedstocks into renewable chemicals and to identify new bacterial lignin-degrading enzymes.

A new species of ferrous-iron-oxidizing, moderately thermophilic, acidophilic bacteria, Acidimicrobium ferrooxidans, has been described. Two isolates of the species differed only in the tendency of one, previously known as strain TH3, to grow in filaments. The chromosomal DNA base composition is between 67 and 69 mol% G + C. The capacity of this species to fix CO2 from air was greater than that of iron-oxidizing thermoacidophiles of the genus Sulfobacillus, which required an enhanced CO2 concentration for optimum autotrophic growth. Under air, ferrous iron oxidation in mixed cultures of A. ferrooxidans with either Sulfobacillus thermosulfidooxidans or Sulfobacillus acidophilus was more extensive than in pure cultures of these three strains. The greater part of ferrous iron oxidation in mixed cultures probably resulted from activity of the Sulfobacillus species, which possess a greater tolerance of ferric iron, and which presumably grew mixotrophically utilizing organic compounds from A. ferrooxidans.