[Temporal and spatial variations and driving factors of phytoplankton in Yongjiang River estuary]. / ç”¬æ±Ÿå£æµ®æ¸¸æ¤ç‰©æ—¶ç©ºåˆ†å¸ƒç‰¹å¾åŠé©±åŠ¨å› å­.

To explore the temporal and spatial variations in phytoplankton community in small estuaries, we collected surface water samples from Yongjiang River estuary during wet, normal, and dry seasons and determined the main driving factors of phytoplankton community. A total of 358 species belonging to nine phyla and 123 genera were identified in all seasons. During wet, normal, and dry seasons, species number was 276, 154 and 151, and the abundance was (170.45±225.43)×103, (51.92±30.28)×103 and (31.65±12.79)×103 cells·L-1, respectively. Diatoms dominated the phytoplankton community, and the main dominant species were Cyclotella meneghiniana, Skeletonema costatum, and Paralia sulcata. Shannon diversity and Pielou evenness indices decreased from inside mouth to outside mouth in wet season, but there was no obvious spatial difference in normal season or dry season. Results of non-metric multidimensional scaling analysis and analysis of similarities showed that phytoplankton community composition differed significantly among different regions (inside, at and outside mouth) and different seasons. In wet season, phytoplankton abundance was significantly positively correlated with temperature, dissolved inorganic nitrogen, and dissolved reactive phosphorus, but significantly negatively correlated with salinity. In normal season, phytoplankton abundance was significantly negatively correlated with temperature. In dry season, it was not significantly correlated with environmental factors. Results of redundancy analysis showed that temperature, salinity, ammonium and dissolved reactive phosphorus explained the variations in phytoplankton community by 19.5%, 11.9%, 9.4% and 8.2%, respectively. These results revealed high dominance of diatoms and the main driving factors (temperature, salinity and nutrients) of phytoplankton community in Yongjiang River estuary.

Muricauda antarctica sp. nov., a marine member of the Flavobacteriaceae isolated from Antarctic seawater.

A Gram-stain-negative, rod-shaped bacterium with appendages, designated Ar-22(T), was isolated from a seawater sample collected from the western part of Prydz Bay, near Cape Darnley, Antarctica. Strain Ar-22(T) grew optimally at 35 °C, at pH 7.5 and in the presence of 1-3% (w/v) NaCl. The isolate was positive for casein, gelatin and Tween 20 decomposition and negative for H2S production and indole formation. Chemotaxonomic analysis showed that MK-6 was the major isoprenoid quinone and phosphatidylethanolamine was the major polar lipid. The major fatty acids were iso-C(17:0) 3-OH, iso-C(15:1) G, iso-C(15:0) and C(16:1)ω7c/iso-C(15:0) 2OH. The genomic DNA G+C content was 44.8 mol%. Comparative 16S rRNA gene sequence analysis revealed that strain Ar-22(T) is closely related to members of the genus Muricauda, sharing 94.2-97.3% sequence similarity with the type strains of species of the genus Muricauda and being most closely related to the Muricauda aquimarina. Phylogenetic analysis based on the 16S rRNA gene sequence comparison confirmed that strain Ar-22(T) formed a deep lineage with Muricauda flavescens. Sequence similarity between strain Ar-22(T) and Muricauda ruestringensis DSM 13258(T), the type species of the genus Muricauda, was 96.9%. Strain Ar-22(T) exhibited mean DNA-DNA relatedness values of 40.1%, 49.4% and 25.7% to M. aquimarina JCM 11811(T), M. flavescens JCM 11812(T) and Muricauda lutimaris KCTC 22173(T), respectively. On the basis of phenotypic and genotypic data, strain Ar-22(T) represents a novel species of the genus Muricauda, for which the name Muricauda antarctica sp. nov. (type strain Ar-22(T) =CGMCC 1.12174(T) = JCM 18450(T)) is proposed.

Citricoccus zhacaiensis sp. nov., isolated from a bioreactor for saline wastewater treatment.

A Gram-positive, neutrophilic, non-motile and non-spore-forming actinobacterium, strain FS24(T), was isolated from a bioreactor treating salt-containing wastewater. This isolate grew in the presence of 0-15 % (w/v) NaCl and at 10-37 degrees C. The optimum NaCl concentration for growth of FS24(T) was 5 % (w/v) at 37 degrees C or 1 % (w/v) at 25 degrees C. Chemotaxonomic analysis revealed MK-9(H(2)) as the predominant menaquinone and the major cellular polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, four unknown glycolipids, two unknown phospholipids and an unknown lipid. The major fatty acids were anteiso-C(15 : 0 ), iso-C(15 : 0), iso-C(16 : 0 ) and anteiso-C(17 : 0). The genomic DNA G+C content was 66.0 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain FS24(T) clustered with members of the genus Citricoccus, exhibiting high sequence similarity to the 16S rRNA gene sequences of the type strains of Citricoccus alkalitolerans (98.9 %) and Citricoccus muralis (98.8 %), respectively. The DNA-DNA relatedness values of strain FS24(T) to C. alkalitolerans DSM 15665(T) and C. muralis DSM 14442(T) were 54 and 39 %, respectively. On the basis of phenotypic and genotypic data, strain FS24(T) represents a novel species of the genus Citricoccus, for which the name Citricoccus zhacaiensis sp. nov. is proposed. The type strain is FS24( T) (=CGMCC 1.7064(T) =JCM 15136(T)).