STUDY OF 14 DENITRIFYING SOIL BACTERIA OF PSEUDOMONAS-STUTZERI GROUP ISOLATED BY ENRICHMENT CULTURE IN PRESENCE OF NITROUS-OXIDE

Abstract

The strains were isolated from soil by enrichment in a liquid miminal medium containing ethanol, acetate, succinate, L-malate or tartrate, under an N2O atmosphere at 32.degree. C. All 14 strains can use the following 25 sources of carbon and energy under aerobic conditions: glycerate, ethanol, propanol, acetate, butyrate, malonate, succinate, glutarate, sebacate, glycollate, L-lactate, D-lactate, L-malate, DL-3-hydroxybutyrate, pyruvate, fumarate, itaconate, mesaconate, crotonate, L-.alpha.-alanine, D-.alpha.-alanine, L-leucine, asparagine, L-tyrosine and L-proline. They hydrolyze Tween 80 but not gelatin. Nitrate is used as nitrogen source. Nitrate reductase A and respiratory nitrite reductase are present. Four of the strains are clearly and easily distinguishable from the others on the basis of 6 characters: special morphology of colonies, in ability to use isovalerate and DL-valine, inability to use glucose, absence of exocellular amylase and high level of metapyrocatechase. Their G + C content is 66-67%. One of the strains is distinct from the others by the yellow pigmentation of its colonies, its ability to use D-glucuronate , trehalose, D-sorbitol and citraconate, ability to grow at 4.degree. but not at 40.degree., and a lower G + C content: 63%. One strain accumulates poly-.beta.-hydroxybutyrate. This work confirms the well known, wide variability of the bacteria belonging to the P. stutzeri group. Denitrification by 2 of the strains was quantitatively studied using cell suspensions. Cells from .**GRAPHIC**. anaerobic cultures reduce .**GRAPHIC**. and NO to N2O and N2; they reduce slowly N2O to N2. Cells grown in anaerobic cultures under N2O also reduce .**GRAPHIC**. and NO to N2O and N2 but they reduce N2O rapidly to N2.