Selection Of Denitrification By Mix-Culturing Fungus-Bacterium And Identification Of Two New Bacteria

Denitrification broadly existed in nature has long been considered as an exclusive trait of bacteria, so the theory of denitrification mechanism mainly came from bacteria in the past years. Bacteria denitrification and the main characteristics of enzymes that catalyze the process were clear. Recently, fungi have been also recognized to perform denitrification. Fungal denitrification shows a unique characteristic that hasn't yet to be identified in bacteria. Bacteria transform nitrate into nitrogen gas, while the major product of fungal denitrification is nitrous oxide. Only a few fungi exhibited in the complete denitrification to nitrogen gas. Fungi appeared to show higher rate of denitrification on the lightly anaerobic condition than bacteria did. The selection mixed-culturing of fungi-bacteria and research of denitrificatin mechanism would provide a new approach to biological denitrificaton. In the study, we had selected three fungi Y, R and F that showed higher denitrification ability, mixed culture with strain HS-03.The mix-culturing fungi-bacteria showed obvious ability to denitrify on slight-anaerobic condition. The optimum cultivating conditions of the mix-culturing fungi-bacteria had been drawn by orthogonal test. The results as follows: T 30癈, pH 8.0, and the optimum source of carbon being succinate. The mechanism of fungi-bacteria mix-culturing and the application for biology denitrification will be explored further.The development and application of molecular biology on microbial identification had advanced in recent years. At present, the sequence of 16SrRNA gave a main basis on studying the systematic development of bacteria and building up the system of microbial taxonomy. The article analyzed the 16SrDNA sequence of two new strains based on the general shape-analysis and biochemical-physiological features. Subsequently the phylogenetic tree was established. The main biochemical and physiological features of HS-1E isolated from the no-nitrogen culture medium were very similar "to that of Serratia andKlebsiella. According to the full-length of 16S rDNA sequence of HS-1E, strain HS-1E was most related to the genus of Serratia sp. The homology of 16S rDNA between HS-1E and S.marcescens was 99.0%. On account of spore-producing Serratia never being reported up to date, HS-1E may be a new species of Serratia. Its identification had certain significance to microbial taxology. The spore-producing mechanism will be studied in the future. The full-length of 16S rDNA sequence of strain HS-G8 was analysed and the result showed that strain HS-G8 was most related to the genus of Arthrobacter. The homologous of nucleartides between HS-G8 and Arthrobacter nicotianae was 99.1%. Since nitrogen- fixtion has not been observed previously among Arthrobacter sp., strain HS-G8 was identified as a new Arthrobacter species that hold the ability of nitrogen-fixtion. The identification would be much important not only to exploit new nitrogen-fixtion bacteria but also to study microbial taxology.