Chemolithoautotrophs

Santini JM, LI Sly, RD Schnagl, JM Macy (2000) A new chemolithoautotrophic arsenite-oxidizing bacterium isolated from a gold mine phylogenetic, physiological and preliminary biochemical studies. Appl Environ Microbiol 66 92-97. 

McCollom, T. M. and E.L. Shock, 1997, Geochemical constraints on chemolithoautotrophic metabolism by microorganisms in seafloor hydrothermal systems. Geochimica Cosmochimica Acta 61,4375 1391. 

In 1958, Peck joined the staff of the enzymology group of the Oak Ridge National Laboratory and continued there to work on sulfur metabolism of chemolithoautotrophic bacteria. In 1965, he was called to Athens. Before moving there, he spent a year in the laboratory of Jacques Senez and Jean LeGall. And then he explored the research niche of hydrogenase and sulfur metabolism, which is a gold mine still today, in various directions. 

The maximal cell density observed under chemolithoautotrophic growth conditions after refeeding twice with hydrogen was 10 cells mlr after... 

Chemolithoautotrophic Hydrogen-Oxidizing and Fe(III)-Reducing Strains Related to the Glucolytic Species... 

Figure 17.1. Phylogenetic tree based on 16S rDNA sequence analysis showing the placement of the novel chemolithoautotrophic Fe(III) reducers. Capital and bold face letters, respiratory Fe(III) reducers , tested heterotrophic species that probably reduce Fe(III) predominantly in an assimilatory fashion.

Table 17.1. Properties of the novel chemolithoautotrophic strains and the corresponding heterotrophic type strains.

Although under chemolithoautotrophic growth conditions, cell densities of only 3-5 x 10 cells per milliliter were observed, the specific rate of Fe(III) reduced per cell unit was about 10 times faster than what had been published for any other Fe(lll) reducer. This strengthens the hypothesis that microbially mediated Fe(III) reduction by obligately anaerobic thermophiles could have been an important process on early Earth, when elevated temperatures were predominant (Baross 1998 Kashefi and Lovley 2000), which includes the involvement in the formation of specific Banded Iron Formations. In light of the properties of the above Fe(lll) reducers, the theories on the origin and biogeochemistry of Banded Iron Formations should be revisited. 

The ability of the chemolithoautotrophic bacteria Thiobacillus ferrooxidans to oxidize Fe has already been utilized for construction of a microbial sensor for the determination of iron [101]. The limit of determination of this biosensor is 60 pmol 1" with a response time ranging from 30 s to 5 min, depending on the Fe +-concentration in the sample. 

This cycle represents the quantitatively most important C02 fixation pathway in Nature. It is found in most aerobic autotrophic organisms, ranging from diverse photosynthetic and chemolithoautotrophic bacteria to chloroplasts of eukaryotic algae and higher plants [5]. It is centered around carbohydrates, with ribulose 1,5-bisphosphate being the C02 acceptor (Figure 3.1). 

Chemolithoautotroph An organism capable of generating metabolically useful energy by the oxidation of inorganic compounds... 

Alcaligenes faecalis and five members of the p Proteobacteria are heterotrophic arsenite oxidizers, whereas Pseudomonas arsenitoxidans and NT-26 grew anaerobically through chemoautotrophic oxidation (Oremland and Stolz, 2005 Santini et al, 2000). However, six members of a Proteobacteria (Ben-5, NT-3, NT-4, NT-2, NT-26, and NT-25) and one member of y Proteobacteria (MLHE-1) were known chemohthoautotrophic arsenite oxidizers (Oremland et al, 2002). The best characterized and probably most studied of aU arsenite oxidizers is Alcaligenes faecalis, a heterotrophic arsenite oxidizer (Osborne and Enrlich, 1976). The arsenite oxidase from Alcaligenes faecalis has been purified and structurally characterized (Ellis et al, 2001). A similar enzyme has also been purified from the heterotrophic arsenite oxidizers Hydrogenophaga sp. strain NT-14 (Vanden Hoven and Santini, 2004) and the chemolithoautotrophic Rhizobium sp. strain NT-26 (Santini and Vanden Hoven, 2004), which indicate that the arsenite oxidase enzyme is also a member of the DMSO reductase family of molybdenum enzymes, similar to the respiratory arsenate reductases (Arr). The arsenite oxidase heterodimer comprises an 88 kDa catalytic subunit encoded by the aoxB gene that contains a [3Fe-4S] cluster and molybdenum bound to the pyranopterin cofactor and a 14 kDa subunit... 

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