Anaerobic growth of halophilic archaeobacteria by reduction of fumarate

Abstract

A number of strains of halophilic archaeobacteria of the genera Halobacterium and Haloferax were able to grow anaerobically using fumarate as electron acceptor. The species showing the best anaerobic growth with fumarate were Haloferax volcanii and Haloferax denitrijicans. The two Haloarcula species tested did not show anaerobic growth enhancement with fumarate. During anaerobic growth of Haloferax trolcanii in the presence of fumarate, succinate accumulated in the medium with a stoichiometry of only 0-16-0-23 mmol succinate per mmol fumarate consumed; this can be explained by the use of succinate for assimilatory purposes. The ability to reduce fumarate to succinate did not correlate with the ability to grow anaerobically using nitrate, dimethylsulphoxide or trimethylamine N-oxide as terminal electron acceptors. Anaerobic respiration with fumarate as electron acceptor supplies the halophilic archaeobacteria with an additional mode of energy generation in the absence of molecular oxygen.

Anaerobic Metabolism in Haloferax Genus

“…gibbonsii (Oren, 1991). The ability to reduce fumarate is not correlated with the ability to reduce nitrate, (per) chlorate, DMSO or TMAO.…”

“…Some members of the Haloferax genus can reduce dimethyl sulphoxide (DMSO), trimethylamine N-oxide (TMAO) (Oren & Trüper, 1990) and fumarate using them as final electron acceptors (Oren, 1991 (Oren & Trüper, 1990). Although the bases of the DMSO and TMAO respiratory systems have not been described for any member or the domain Archaea, some studies revealed that the genetic machineries involved in two pathways are closely related in haloarchaea (Müller & DasSarma, 2005).…”

“…Most of these species generally grow chemo-organotrophically thanks to a respiratory chain that enables them to use oxygen as electron acceptor (Oren, 1991). Nevertheless, some species have facultative anaerobic capabilities (DasSarma & Arora 2002).…”

“…In general terms, Haloferax growth under those microaerobic or even strict anaerobic conditions is possible because oxygen is replaced by other final electron acceptors such us nitrate, nitrite (Lledó, Martinez-Espinosa, Marhuenda-Egea & Bonete, 2004;Bonete et al, 2008;Nájera-Fernández, Zafrilla, Bonete & Martinez-Espinosa, 2012;Esclapez, Zafrilla, Martinez-Espinosa & Bonete, 2013) (per)chlorate (Oren, Elevi-Bardavid & Mana, 2014; Martínez-Espinosa, Richardson & Bonete, 2015), sulphur or sulphide (Elshahed et al, 2004), arsenate (Rascovan, Maldonado, Vazquez & Eugenia Farias, 2015), dimethyl sulfoxide (DMSO), trimethylamine N-oxide (TMAO) and fumarate (Oren & Trüper, 1990;Oren, 1991;Oren, 1999;Müller & DasSarma, 2005).…”

Elemental sulfur and acetate can support life of a novel strictly anaerobic haloarchaeon

“…According to physiological and genomic studies, cultivated haloarchaea are predominantly aerobic heterotrophs (Andrei et al, 2012). There are only a few known examples of facultative anaerobic haloarchaea species capable of growth by either fermentation, or anaerobic respiration using nitrate, fumarate, dimethyl sulfoxide or trimethylamine N-oxide as terminal electron acceptors (Oren and Trüper, 1990;Oren, 1991;Antunes et al, 2008;Bonete et al, 2008;Werner et al, 2014). As these electron acceptors are present in hypersaline anoxic habitats at very low concentrations (Oren, 2011), it might appear that these facultative anaerobes cannot play a significant role in anaerobic environments.…”