Isolation, Characterization and Autotrophic Metabolism of a Moderately Thermophilic Carboxydobacterium, Pseudomonas thermocarboxydovorans sp. nov.

Abstract

Three strains of Gram-negative, obligately aerobic, moderately thermophilic, CO-utilizing bacteria have been isolated by enrichment at 45-55 "C in mineral medium under CO, H2 and air. The properties of the strains, designated C2, S1 and FE, suggest that they should be included in a single species that we have named Pseudomonas thermocarboxydovorans. The isolates can grow on CO and a limited range of organic and amino acids; neither sugars nor H2/C02 support growth and €I2 is not oxidized. Strain C2 contains a soluble, inducible C0:phenazine ethosulphate oxidoreductase, lacks hydrogenase and assimilates CO via ribulose bisphosphate carboxylase. The organism apparently contains a mechanism for assimilating phosphoglycollate. Pseudomonas carboxydovorans, P . carboxydoflava, P . carboxydohydrogena, P . gazotropha,Cornomonas compransoris and Achromobacter carboxydus, can utilize CO as sole carbon and energy source (Kim & Hegeman, 1983;Meyer & Schlegel, 1983). These bacteria are Gramnegative, mostly mesophilic and, with the exception of A . carboxydus, able to grow autotrophically with hydrogen (H,) and carbon dioxide (CO,). This paper describes the isolation, characterization and growth of three strains of a novel thermophilic species of carboxydobacterium.Abbreviations: API 20E, API ZYM and API 5OCH refer to the bacteriological test strips supplied by API Laboratory Products, Grafton Way, Basingstoke, Hants, UK ; PES, phenazine ethosulphate; PHB, poly-Qhydroxybutyrate; DCPIP, 2,6-dichlorophenolindophenol.

Microbial growth on carbon monoxide

“…bacteria capable of aerobic and chemolithoautotrophic growth on CO, are not closely related among themselves, but this metabolic type is established in species of different taxonomic position (Meyer & Schlegel 1983;Meyer et al 1986). With the exception of Pseudomonas thermocarboxydovorans (Lyons et al 1984), Bacillus schlegelii (Krfiger & Meyer 1984), and Streptomyces thermoautotrophicus ), carboxidotrophs are mesophilic organisms. In contrast to nitrifying, hydrogen-, iron-, or sulfur-oxidizing bacteria, carboxidotrophic organisms are able to generate their own CO2 needed for assimilation.…”

“…108 metric tons. year -1 (Lyons et al 1984) and with increasing industry and traffic the amount of CO production is increasing rapidly. Conrad (1988) reported recent data on the production of CO due to anthropogenic (16.4 + 8-108), biospheric (1.92 + 1.2.…”

Biochemistry and physiology of aerobic carbon monoxide-utilizing bacteria

“…These are, specifically, a CO-insensitive mode of Table 1 Summary of species of carboxydotrophic bacteria known to date and some of their properties ' Reference to isolation and properties of strains has been made in recent articles and reviews [4,7,9,18,83]. b The values for G+C contents [1,4,24,32,39,86] and for quinone contents [4,32,86] contain data communicated by G. Auling. Q, ubiquinone; MK, menaquinone.…”

“…The anabolic function of CO dehydrogenase is to provide CO 2 for assimilation by ribulose-l,5bisphosphate carboxylase [4,9,14]. Operation of .the Calvin cycle during growth with CO is a general property of all carboxydotrophic bacteria obtained to date, and has also been established for the recently isolated Pseudomonas therrnocarboxydovorans [24]. It has been shown [25] that CO 2, not bicarbonate, is the substrate for ribulose-1,5-bisphosphate carboxylase.…”

The redox centers in the molybdo iron-sulfur flavoprotein CO dehydrogenase from the thermophilic carboxidotrophic bacteriumPseudomonas thermocarboxydovorans

“…Bacterial cell mass was produced with CO as the substrate under chemolithoautotrophic conditions in 70‐l fermenters filled with 50 l of a mineral medium of pH 7.2 plus trace element solution TS2 containing ammonium Fe(III) citrate (0.1 g l −1 ) and ammonium chloride (5 g l −1 ) [12]. O. carboxidovorans OM5 (DSM 1227) was grown at 30°C [12] and P. thermocarboxydovorans strain C2 (NCIB 11893) at 50°C [13].…”