Halothermothrix orenii

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Bacteria; Firmicutes; Clostridia; Halanaerobiales; Halanaerobiaceae; Halothermothrix; Halothermothrix orenii

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 stresses. A halophilic, thermophilic, anaerobic, and fermentative bacterium, these types of organisms show to be rare in nature even after intensive search (Patel et al). H. orenii can be useful sources of enzymes with biotechnological applications such as sugar processing and hydrolysis after chemical treatment which usually occurs at high temperatures and results in high concentrations of salt (Patel et al). Being halophilic, it 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 bioremediation of oil fields (Patel et al).

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 majorities of genes are transcribed on the leading strand (89%) and is among one of the highest percentages in bacterial genomes (Mavromatis et al 2009).

Cell Structure, Metabolism and Life Cycle

Halothermothrix orenii is generally a gram-negative bacterium, but 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 secrtion 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. Furthermore, it is a high hydrogen producer, useful for bioremediation of hot salty oil fields, and it produces thermohalophilic enzymes with a potential for use in biotechnology.


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%.


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.


Page authored by Jacob Prusakiewicz, student of Prof. Jay Lennon at Michigan State University.