3) has an important ecological implication and deserves special attention. This is the only organism known so far that is capable of such a function under soda-saturated conditions among sulfidogens from soda lakes. Although the

pathway of acetate utilization needs to be studied in detail, one of the possibilities is that it might be used by reversing the acetogenic Wood cycle. A test for the ability of the type species N. acetigena to grow by sulfur respiration either organotrophically with EtOH or lactate or lithotrophically with H2 and formate yielded negative results. Thus, significant physiological differences within a single phylotype highlight the necessity of combining molecular ecology with the isolation and physiological selleck screening library investigation of pure cultures in order to understand the function of microbial communities. In other words, multiple closely related phylotypes detected using a culture-independent

approach may correspond to physiological diversification and, therefore, both aspects need to be studied in parallel. A recent example of such a trait has been revealed by an extensive polyphasic analysis of two extremely halophilic members of Salinibacter ruber (Peña et al., 2010). Fermentative members of the order Halanaerobiales dominate the anaerobic bacterial community under hypersaline conditions due to their relatively ‘cheap’ K+-based osmoadaptation strategy (Oren, 1999, 2011). According to the hypothesis of A. Oren, in prokaryotes, there is a direct correlation between the energy yield of catabolism and the ability NVP-BKM120 molecular weight to grow at high salinity. Because the inorganic osmolyte strategy based on potassium import needs much less energy input than de novo synthesis of organic osmolytes, it confers an advantage to such organisms to exploit low energy yield catabolic reactions at extreme salinity. On the basis of the work presented here and also based on other recently published results, it seems that some members of the order Haloanaerobiales use an energy metabolism that has until now been considered rather uncharacteristic for this group. In the absence

of more Calpain specialized extremely halophilic dissimilatory sulfur-dissimilatory respirers, these organisms are able to perform anaerobic respiration in addition to or even instead of fermentation. Such examples are represented by the extremely halophilic Selenihalanaerobacter shriftii (Switzer-Blum et al., 2001), the recently described extremely haloalkaliphilic arsenate- and sulfur-reducing Halarsenatibacter silvermanii (Switzer-Blum et al., 2009) and the Natroniella strains AHT3, AHT4 and AHT18, described here. The latter, however, advanced further in their specialization by adopting a lithoautotrophic lifestyle. Both possibilities (autotrophy and respiratory catabolism) are basically present in some of the nonextremophilic acetogens.