K-051. To Denitrify or not to Denitrify? That’s the Question for Gram-Positive Bacteria

P. De Vos, I. Verbaendert, K. Heylen;
Ghent Univ., Gent, BELGIUM.

Limited reliable information is available on the distribution of denitrification amongst bacteria in general and amongst Gram-positive bacteria in particular. One of the major problems is the shortage of correct information concerning the nitrogen reduction characteristics in novel bacterial species descriptions. If available, the nature and quality of the tests is often poor and limited to miniaturised API tests. Let us take Bacillus as an example. It has been known for decades that the genus Bacillus has denitrifying representatives (e.g. B. licheniformis). However, notwithstanding their great potential for wastewater treatment and their great impact in food industries, members of Bacillus are neglected for their impact in the denitrification process. Therefore the prevalence of the denitrification capacity within the genus Bacillus is largely unknown. Indeed, in the contribution on the genus in Bergey’s Manual of Systematic Bacteriology (Vol. three), ‘anaerobic growth’ and ‘nitrate reduced to nitrite’ is mentioned without any further specification of the process. It is to be expected that further in-depth phenotypic and genotypic research of Bacillus strains will reveal the real prevalence of denitrification in this genus pointing to so far unknown denitrifying Bacillus species, as will be the case for other Gram-positive taxa. We have phenotypically screened type strains of 87 of the 146 present valid species of Bacillus for their capacity to denitrify. Subsequently, within several selected species a diverse set of strains was analyzed. Preliminary data showed an unexpected high prevalence of the denitrification trait within Bacillus. However, the present knowledge of denitrification genes did not allow the straightforward detection of the genes that are involved in the Bacillus denitrification capacities.