Halothermothrix orenii

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Classification

Bacteria (Domain); Firmicutes (Phylum); Clostridia (Class); Halanaerobiales (Order); Halanaerobiaceae (Family); Halothermothrix (Genus); H. orenii (Species)

Phase-contrast photomicrograph of strain H168. Bar = 10 (1)

Description and Significance

Halothemothrix orenii, of the order Haloanaerobiales, was named in honor of Aharon Oren, who made important contributions to the understanding of halophilic anaerobic bacteria. H. orenii is unique amongst extremophiles as they have adapted to more than one environmental stress. A halophilic, thermophilic, anaerobic, and fermentative bacterium, these types of organisms show to be rare in nature even after extensive search. H. orenii can be a useful source of enzymes with biotechnological applications. One such application is in sugar processing, which usually occurs at high temperatures and results in high concentrations of salt. Being halophilic and thermophilic, the organism can provide insights into the adaptations of proteins and metabolic pathways to produce this phenotype. This bacterium is also of particular significance because of its ability to manufacture hydrogen and is used in the bioremediation of hot, salty oil fields.

Genome Structure

This is the first genome sequence of an organism belonging to the Haloanaerobiales. Sequence analysis 16S rRNA studies have placed this organism in the order Haloanaerobiales in the phylum Firmicutes (low G+C/gram positive). The complete sequence revealed that the genome consists of one circular chromosome of 2,578,146 bps encoding 2451 predicted genes and a GC content of 38%. The majority of genes are transcribed on the leading strand (89%), and this is among one of the highest percentages in bacterial genomes.

Cell Structure, Metabolism and Life Cycle

Halothermothrix orenii is generally a gram-negative bacterium, but it has been shown to contain a number of sporulation genes that are often gram-positive. The cells are long, flexible rods, mainly occurring singly with dimensions of 10 to 20 by 0.4 to 0.6 micrometers. Colonies are yellow, flat, and circular with diameters ranging from 0.5 to 1.0 millimeters. The organism is unique among firmicutes in possessing outer membrane secretion proteins of the secretin family on its outer membrane. H. orenii is chemoorganotrophic. It contains all the enzymes necessary for glycolytic degradation of monosaccharides. A large variety of sugars components can be used as energy sources, and genes involved in the metabolism of cellobiose, starch, glucose, galactose, fructose, fucose, xylose, ribose, and citrate were identified. H. orenii is able to synthesize all amino acids except for tryptophan de novo.

Ecology

Halothermothrix orenii was isolated from sediment of a Tunisian salt lake. It is a strict anaerobe with a preference for hot, salty environments. In lab tests, optimal growth occurs around 60 degrees celius, with concentrations of NaCl around 10%. H. orenii has been shown to be rare in nature, but researchers believe that the salt lakes of Australia, Africa and the Middle East, as well as petroleum reservoirs, would be likely habitats where the organism could thrive.

Biotechnology Implications

H. orenii is important for its biotechnological applications. For instance, it has been used in the bioremediation of hot salty oil fields. Furthermore, all four of its proteins easily crystallize, making it useful for pharmaceutical purposes. Also, it is a high hydrogen producer, and hydrogen is being looked at as an alternative energy source. Because H. orenii is one of the only classified halophilic and thermophilic organisms, its enzymes are thought to be important for biotechnology in this extreme environment. More research would be useful in this area.

References

1. Cayol JL, Ollivier B, Patel BK, Prensier G, Guezennec J, et al. (1994) Isolation and characterization of Halothermothrix orenii gen. nov., sp. nov., a halophilic, thermophilic, fermentative, strictly anaerobic bacterium. Int J Syst Bacteriol 44: 534–540.

2. Mavromatis, Konstantinos, Natalia Ivanova, Iain Anderson, Athanasios Lykidis, Sean D. Hooper, Hui Sun, Victor Kunin, Alla Lapidus, Philip Hugenholtz, Bharat Patel, and Nikos C. Kyrpides. "Genome Analysis of the Anaerobic Thermohalophilic Bacterium Halothermothrix orenii." PLoS One 4 (2009): E4192.

3. Mijts, BN, and BKC Patel. "Random sequence analysis of genomic DNA of an anaerobic, thermophilic, halophilic bacterium, Halothermothrix orenii." Extremophiles 5 (2001): 61-69.

Author

Page authored by Jacob Prusakiewicz and Anne Otwell, students of Prof. Jay Lennon at Michigan State University.