Unraveling microbe-mediated degradation of lignin and lignin-derived aromatic fragments in the Pearl River Estuary sediments.

Estuaries are one of the most crucial areas for the transformation and burial of terrestrial organic carbon (TerrOC), playing an important role in the global carbon cycle. While the transformation and degradation of TerrOC are mainly driven by microorganisms, the specific taxa and degradation processes involved remain largely unknown in estuaries. We collected surface sediments from 14 stations along the longitudinal section of the Pearl River Estuary (PRE), P. R. China. By combining analytical chemistry, metagenomics, and bioinformatics methods, we analyzed composition, source and degradation pathways of lignin/lignin-derived aromatic fragments and their potential decomposers in these samples. A diversity of bacterial and archaeal taxa, mostly those from Proteobacteria (Deltaproteobacteria, Gammaproteobacteria etc.), including some lineages (e.g., Nitrospria, Polyangia, Tectomicrobia_uc) not previously implicated in lignin degradation, were identified as potential polymeric lignin or its aromatic fragments degraders. The abundance of lignin degradation pathways genes exhibited distinct spatial distribution patterns with the area adjacent to the outlet of Modaomen as a potential degradation hot zone and the Syringyl lignin fragments, 3,4-PDOG, and 4,5-PDOG pathways as the primary potential lignin aromatic fragments degradation processes. Notably, the abundance of ferulic acid metabolic pathway genes exhibited significant correlations with degree of lignin oxidation and demethylation/demethoxylization and vegetation source. Additionally, the abundance of 2,3-PDOG degradation pathways genes also showed a positive significant correlation with degree of lignin oxidation. Our study provides a meaningful insight into the microbial ecology of TerrOC degradation in the estuary.

Discordance Between Resident and Active Bacterioplankton in Free-Living and Particle-Associated Communities in Estuary Ecosystem.

Bacterioplankton are the major driving force for biogeochemical cycles in estuarine ecosystems, but the communities that mediate these processes are largely unexplored. We sampled in the Pearl River Estuary (PRE) to examine potential differences in the taxonomic composition of resident (DNA-based) and active (RNA-based) bacterioplankton communities in free-living and particle-associated fractions. MiSeq sequencing data showed that the overall bacterial diversity in particle-associated fractions was higher than in free-living communities. Further in-depth analyses of the sequences revealed a positive correlation between resident and active bacterioplankton communities for the particle-associated fraction but not in the free-living fraction. However, a large overlapping of OTUs between free-living and particle-associated communities in PRE suggested that the two fractions may be actively exchanged. We also observed that the positive correlation between resident and active communities is more prominent among the abundant OTUs (relative abundance > 0.2%). Further, the results from the present study indicated that low-abundance bacterioplankton make an important contribution towards the metabolic activity in PRE.

Algicidal Activity of Streptomyces eurocidicus JXJ-0089 Metabolites and Their Effects on Microcystis Physiology.

UNLABELLED: Copper sulfate (CuSO4) has been widely used as an algicide to control harmful cyanobacterial blooms (CyanoHABs) in freshwater lakes. However, there are increasing concerns about this application, due mainly to the general toxicity of CuSO4 to other aquatic species and its long-term persistence in the environment. This study reported the isolation and characterization of two natural algicidal compounds, i.e., tryptamine and tryptoline, from Streptomyces eurocidicus JXJ-0089. At a concentration of 5 µg/ml, both compounds showed higher algicidal efficiencies than CuSO4 on Microcystis sp. FACHB-905 and some other harmful cyanobacterial strains. Tryptamine and tryptoline treatments induced a degradation of chlorophyll and cell walls of cyanobacteria. These two compounds also significantly increased the intracellular oxidant content, i.e., superoxide anion radical (O2 (-)) and malondialdehyde (MDA), but reduced the activity of intracellular reductants, i.e., superoxide dismutase (SOD), of cyanobacteria. Moreover, tryptamine and tryptoline treatments significantly altered the internal and external contents of microcystin-LR (MC-LR), a common cyanotoxin. Like CuSO4, tryptamine and tryptoline led to releases of intracellular MC-LR from Microcystis, but with lower rates than CuSO4 Tryptamine and tryptoline (5 µg/ml) in cyanobacterial cultures were completely degraded within 8 days, while CuSO4 persisted for months. Overall, our results suggest that tryptamine and tryptoline could potentially serve as more efficient and environmentally friendly alternative algicides than CuSO4 in controlling harmful cyanobacterial blooms. IMPORTANCE: Cyanobacterial harmful algal blooms (CyanoHABs) in aquatic environments have become a worldwide problem. Numerous efforts have been made to seek means to prevent, control, and mitigate CyanoHABs. Copper sulfate (CuSO4), was once a common algicide to treat and control CyanoHABs. However, its application has become limited due to concerns about its general toxicity to other aquatic species and its long-term persistence in the environment. There is a great need for algicides with higher specificity and low environmental impacts. This study reports the isolation and characterization of two natural algicidal compounds from a streptomycete strain, Streptomyces eurocidicus JXJ-0089. Our results suggest that the identified algicides could potentially serve as more efficient and environmentally friendly alternative algicides than CuSO4 in controlling harmful cyanobacterial blooms.

Actinophytocola gilvus sp. nov., isolated from desert soil crusts, and emended description of the genus Actinophytocola Indananda et al. 2010.

An actinomycete strain, designated I12A-02593(T), was isolated from a desert soil crust sample collected in the Shapotou region of Tengger Desert, north-west China. The isolate grew well on International Streptomyces Project (ISP) media 2, 3, 5 and 7, YS and Bennett's agar; it produced spherical bodies and formed clumps on the aerial mycelia on ISP 5 agar plates. Chemotaxonomically, the strain contained meso-diaminopimelic acid as the diagnostic diamino acid, arabinose and galactose as the diagnostic sugars in whole-cell hydrolysates, MK-9(H4) as the sole isoprenoid quinone, and iso-C16 : 0, iso-C16 : 0 2-OH and iso-C16 : 1 H as the major cellular fatty acids, without mycolic acids. The profile of the phospholipids mainly comprised diphosphatidylglycerol, phosphatidylethanolamine and hydroxyphosphatidylethanolamine. The genomic DNA G+C content was 70.1 mol%. The 16S rRNA gene sequence of strain I12A-02593(T) exhibited 96.4-97.4 % similarities with members of the genus Actinophytocola. In the phylogenetic tree based on 16S rRNA gene sequences, the isolate formed a robust cluster with Actinophytocola oryzae NBRC 105245(T), Aactinophytocola timorensis NBRC 105524(T), Actinophytocola corallina NBRC 105525(T), Actinophytocola burenkhanensis NBRC 105883(T)and Actinophytocola xinjiangensis NBRC 106673(T). DNA-DNA hybridization values between strain I12A-02593(T) and the five species of the genus Actinophytocola were all less than 70 %. On the basis of the polyphasic taxonomy evidence, a novel species of the genus Actinophytocola is proposed, with the name Actinophytocola gilvus sp. nov. The type strain is I12A-02593(T) ( = CPCC 203543(T) = DSM 45828(T) = NBRC 109453(T) = KCTC 29165(T)). An emended description of the genus Actinophytocola is also provided.

Roseivivax roseus sp. nov., an alphaproteobacterium isolated from a solar saltern soil sample.

A pink, Gram-stain-negative, motile, halotolerant bacterium with subpolar flagellum, designated strain BH87090T, was isolated from a saline soil sample collected from the south-west coastal area of South Korea (125° 58' 58.08″ E 34° 45' 37.32″ N). The isolate formed opaque pink to red colonies on marine agar plates at 30 °C. The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, sulfoquinovosyl diacylglycerol, phosphatidylcholine and one unidentified phospholipid. The sole respiratory quinone was ubiquinone-10 (Q-10). The major cellular fatty acids were C18:1ω7c, C19:0 cyclo ω8c, C16:0 and 11-methyl C18:1ω7c. The genomic DNA G+C content was 61.8 mol%. These chemotaxonomic characteristics were all consistent with specific properties of the genus Roseivivax. Phylogenetic analysis based on 16S rRNA gene sequences showed that the isolate affiliated to the cluster with members of the genus Roseivivax in the Roseobacter clade, which suggested that the strain belonged to the genus Roseivivax. However, the low 16S rRNA gene similarities (93.5-95.3%) of strain BH87090T with all the members of the genus Roseivivax indicated that it represented a novel species of the genus Roseivivax. On the basis of phenotypic and genotypic data, strain BH87090T should be classified as a novel species of the genus Roseivivax. The name Roseivivax roseus sp. nov. is proposed, with strain BH87090T (=DSM 23042T=KCTC 22650T) as the type strain.