Oxygen tolerance of strictly aerobic hydrogen-oxidizing bacteria

Abstract

Growth of various bacteria, especially aerobic hydrogen-oxidizing bacteria, in the presence of 2 to 100% (v/v) oxygen in the gas atmosphere was evaluated. The bacterial strains included Alcaligenes eutrophus, A. paradoxus, Aquaspirillum autotrophicum, Arthrobacter spec. strain 11 X, Escherichia coli, Arthrobacter globiformis, Nocardia opaca, N. autotrophica, Paracoccus denitrificans, Pseudomonas facilis, P. putida, and Xanthobacter autotrophicus. Under heterotrophic conditions with fructose or gluconate as substrates neither colony formation on solid medium nor the growth rates in liquid media were drastically impaired by up to 100% oxygen. In contrast, autotrophic growth--with hydrogen, carbon dioxide and up to 80% oxygen in the gas atmosphere--was strongly depressed by high oxygen concentrations. However, only the growth rate, not the viability of the cells, was decreased. Growth retardation was accompanied by a decrease of hydrogenase activity.

Effect of Hydrogen, Sucrose and Oxygen on Uptake Hydrogenase in Nitrogen-fixing and Ammonium-grown Pseudomonas saccharophila ATCC 15946

“…saccharophila was not sensitive to 0, and in this respect resembles the H2 uptake system of Aquaspirillum autotrophicum, Alcaligenes eutrophus and Azospirillum arnazonense (Aragno & Schlegel, 1978;Fu & Knowles, 1986;Wilde & Schlegel, 1982) but differs from that of other diazotrophic bacteria such as Azospirillum brasilense and Azospirillum lipoferum (Fu & Knowles, 1986;Pedrosa et al, 1982;Tibelius & Knowles, 1983), and Rhizobium japonicum and its bacteroids (Maier et al, 1979;Ruiz-Argueso et al, 1979). However, 18% 0, partially repressed hydrogenase formation.…”

RubisCO selection using the vigorously aerobic and metabolically versatile bacterium Ralstonia eutropha

“…This strain failed to support autotrophic CO 2 -dependent growth. Because heterotrophic growth on fructose partially de-represses cbb gene expression [24], the deletion strain was grown on fructose medium to confirm unperturbed expression of other cbb genes. However, the cell extracts lacked PRK activity (Table 1).…”

“…Owing to the anaerobic assay conditions employed in this study, the wild-type enzyme’s K m value for CO 2 (K c ; 34 μM) is significantly lower than 66 μM, which was obtained from aerobic assays (i.e., with ~21% O 2 ) [35]. Besides having a K c value similar to that of plant RubisCOs, the wild-type enzyme’s high K o value (947 μM) (Table 3), which is close to the concentration of an atmosphere saturated with O 2 (~1200 μM), likely accounts for this enzyme’s ability to support CO 2 -dependent growth of R. eutropha in the presence of gas mixtures with up to 80% oxygen [24]. …”

“…However, a few bacteria like R. eutropha , which do not have any discernible means to protect RubisCO from O 2 , can still fix CO 2 and grow efficiently under rigorous aerobic growth conditions [24]. The genetics and control of CO 2 -assimilation has been well studied in R. eutropha .…”

“…Strain HF210 is a spontaneous megaplasmid pHG1-free derivative of strain H16, which is capable of organoautotrophic growth with formate as both the carbon and energy source. But the absence of hydrogenases (encoded by pHG1 in strain H16) renders the strain incapable of supporting O 2 - and CO 2 -dependent growth with H 2 as the sole source of energy, despite strong indications that the expression of cbb genes from cbb c is derepressed [24, 28]. Strain HB10 was derived from strain HF210 by the insertion of transposon Tn5 within cbbL c and thus cannot support autotrophic growth.…”