Electroanalytical characterization of the direct Marinobacter hydrocarbonoclasticus nitric oxide reductase-catalysed nitric oxide and dioxygen reduction

Marinobacter panjinensis sp. nov., a moderately halophilic bacterium isolated from sea tidal flat environment

Two moderately halotolerant bacterium strains, designated PJ-16^T and PJ-38, were isolated from a tidal flat of the red beach in Panjin City, Liaoning Province, PR China. Cells were found to be Gram-stain-negative, aerobic, motile, rod-shaped with a single polar flagellum. Optimum growth of strain PJ-16^T occurred at 30 °C, pH 7.0 and 0.2-8.0  % (w/v) NaCl, and strain PJ-38 at 30 °C, pH 6.0-7.0 and 0.2-8.0  % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain PJ-16^T was most closely related to Marinobacter denitrificans KCTC 62941^T (99.2 % 16S rRNA gene sequence similarity), Marinobacter algicola DSM 16394^T (98.6 %), Marinobacter salarius JCM 19399^T (98.4 %) and Marinobacter confluentis KCTC 42705^T (98.2 %), and strain PJ-38 was most closely related to M. denitrificans KCTC 62941^T (99.1 %), M. algicola DSM 16394^T (98.6 %), M. salarius JCM 19399^T (98.4 %) and M. confluentis KCTC 42705^T (98.1 %). The G+C content of the genomic DNA of strain PJ-16^T based on its draft genomic sequence was 57.4 mol%. The major cellular fatty acids of strain PJ-16^T were C_16 : 0, C_16 : 1  ω7c/C_16 : 1  ω6c and C_18 : 1  ω9c. The major respiratory quinone of PJ-16^T was ubiquinone-9 and the major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol. The results of the phenotypic, phylogenetic and genomic analyses revealed that strains PJ-16^T and PJ-38 represent a novel species of the genus Marinobacter, and the name Marinobacter panjinensis sp. nov. is proposed. The type strain is PJ-16^T (= CGMCC 1.13694^T= KCTC 72023^T).

A fungus-bacterium co-culture synergistically promoted nitrogen removal by enhancing enzyme activity and electron transfer

The fungus Penicillium citrinum WXP-2 and the bacterium Citrobacter freundii WXP-9 were isolated and found to have poor denitrification performance. Surprisingly, co-culture of the two strains which formed fungus-bacterium pellets (FBPs) promoted the removal efficiency of nitrate (NO₃^--N; 95.78%) and total nitrogen (TN; 81.73%). Nitrogen balance analysis showed that excess degraded NO₃^--N was primarily converted to N₂ (77.53%). Moreover, co-culture increased the dry weight to 0.74 g/L. The diameter of pellets and cell viability also increased by 1.49 and 1.78 times, respectively, indicating that the co-culture exerted a synergistic effect to promote growth. The increase in electron-transmission system activity [99.01 mg iodonitrotetrazolium formazan/(g·L)] and nitrate reductase activity [8.65 mg N/(min·mg protein)] were responsible for denitrification promotion. The FBPs also exhibited the highest degradation rate at 2:1 inoculation ratio and 36 h delayed inoculation of strain WXP-9. Finally, recycling experiments of FBP demonstrated that the high steady TN removal rate could be maintained for five cycles.

Marinobacter denitrificans sp. nov., isolated from marine sediment of southern Scott Coast, Antarctica

A novel bacterium, designated JB02H27^T, was isolated from marine sediment collected from the southern Scott Coast, Antarctica. Cells were Gram-stain-negative, facultatively anaerobic, polar-flagellated and motile rods. Growth occurred at 4-45 °C, at pH 7.0-9.0 and with 3-25 % (w/v) NaCl. Phylogenetic trees based on 16S rRNA gene sequences showed that strain JB02H27^T consistently fell within the genus Marinobacter and formed a clade together with Marinobacter algicola DG893^T (98.8 % similarity), Marinobacter confluentis KCTC 42705^T (98.4 %), Marinobacter salarius R9SW1^T (98.4%) and Marinobacter halotolerans CP12^T (97.9 %), which were subsequently used as reference strains for comparisons of phenotypic and chemotaxonomic characteristics. Average nucleotide identity values between strain JB02H27^T and the four related type strains were 80.9, 76.6, 81.9 and 76.3 %, respectively. The major fatty acids were summed feature 3, C_16 : 0, C_18 : 1 ω9c and C_16 : 0 N alcohol. The polar lipids included phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, and an unidentified phospholipid, aminolipid, aminophospholipid and glycolipids. The sole respiratory quinone was ubiquinone-9. The DNA G+C content was 56.9 mol%. Based on the genomic, phylogenetic, phenotypic and chemotaxonomic analysis, we propose that strain JB02H27^T represents a novel species of the genus Marinobacter, for which the name Marinobacter denitrificans sp. nov. is proposed. The type strain is JB02H27^T (=GDMCC 1.1528^T=KCTC 62941^T).