Performance, kinetic characteristics and bacterial community of short-cut nitrification and denitrification system at different ferrous ion conditions.

In order to explore the operation performance, kinetic characteristics and bacterial community of the short-cut nitrification and denitrification (SND) system, the SND system with pre-cultured short cut nitrification and denitrification sludge was established and operated under different ferrous ion (Fe (II)) conditions. Experimental results showed that the average NH4+-N removal efficiency (ARE) of SND system was 97.3% on Day 5 and maintained a high level of 94.9% ± 1.3% for a long operation period. When the influent Fe(II) concentration increased from 2.3 to 7.3 mg L-1, the sedimentation performance, sludge concentration and organic matter removal performance were improved. However, higher Fe(II) of 12.3 mg L-1 decreased the removal of nitrogen and CODCr with the relative abundance (RA) of Proteobacteria and Bacteroidetes decreased to 30.28% and 19.41%, respectively. Proteobacteria, Bacteroidetes and Firmicutes were the dominant phyla in SND system. Higher Fe(II) level of 12.3 mg L-1 increase the RA of denitrifying genus Trichococcus (33.93%), and the denitrifying genus Thauera and Tolumonas dominant at Fe(II) level of no more than 7.3 mg L-1.

Exposure to trace levels of live seaweed-derived antibacterial 2,4,6-tribromophenol modulates ß-lactam antibiotics resistance in Vibrio.

Non-antibiotic substances have been found to contribute to the spread of antibiotic resistance. Bromophenols (BPs) are special anti-bacterial substances obtained from seaweed. This study explored the modulatory effect of trace BPs from a live seaweed on the antibiotic resistance of pathogenic Vibrio (V.) strains. A hydroponic solution of Ulva fasciata was found to contain trace levels (9-333 µg L-1) of 2,4,6-tribromophenol (TBP), a typical BP. TBP at a concentration of 165 µg L-1 significantly increased the inhibition zone diameter of widely used ß-lactam antibiotics (amoxicillin and ampicillin) against V. alginolyticus M7 (Va. M7) and V. parahaemolyticus M3 (Vp. M3) as well as reduced the minimum inhibitory concentration by 2-4 fold against Va. M7. Whole genome re-sequencing analysis demonstrated that Va. M3 (53-60) had more mutant genes than Vp. M7 (44) in ß-lactam resistance pathway. Transcriptome sequencing analysis, along with verification through RT-qPCR, further showed that oligopeptide permease (opp) was the only differentially expressed gene (DEG) among the mutated genes in the ß-lactam resistance pathway. The opp transport activity and membrane permeability of Vibrio were both enhanced at 165 µg L-1 of TBP, and the ability of biofilm formation was also decreased. Thus, antibiotics resistance improvement of Vibrio by TBP was potentially related with the promoted opp transport activity, membrane permeability and inhibited biofilm formation.

A collaborative effect of solid-phase denitrification and algae on secondary effluent purification.

This study explored the collaborative effect on nutrients removal performance and microbial community in solid-phase denitrification based bacteria-algae symbiosis system. Three biodegradable carriers (apple wood, poplar wood and corncob) and two algae species (Chlorella vulgaris and Chlorella pyrenoidosa) were selected in these bacteria-algae symbiosis systems. Results demonstrated that corncob as the carrier exhibited the highest average removal efficiencies of total nitrogen (83.7%-85.1%) and phosphorus removal (38.1%-49.1%) in comparison with apple wood (65.8%-71.5%, 25.5%-32.7%) and poplar wood (42.5%-49.1%, 14.2%-20.7%), which was mainly attributed to the highest organics availability of corncob. The addition of Chlorella acquired approximately 3%-5% of promotion rates for nitrated removal among three biodegradable carriers, but only corncob reactor acquired significant promotions by 3%-11% for phosphorous removal. Metagenomics sequencing analysis further indicated that Proteobacteria was the largest phylum in all wood reactors (77.1%-93.3%) and corncob reactor without Chlorella (85.8%), while Chlorobi became the most dominant phylum instead of Proteobacteria (20.5%-41.3%) in the corncob with addition of Chlorella vulgaris (54.5%) and Chlorella pyrenoidosa (76.3%). Thus, the higher organics availability stimulated the growth of algae, and promoted the performance of bacteria-algae symbiosis system based biodegradable carriers.

Simultaneous denitrification and organics removal by denitrifying bacteria inoculum in a multistage biofilm process for treating desulfuration and denitration wastewater.

This study aimed to treat real wastewater from the desulfuration and denitration process in a petrochemical plant with high-strength nitrogen (TN≈200 mg/L, > 90% nitrate), sulfate (2.7%) and extremely low-strength organics (CODCr < 30 mg/L). Heterotrophic denitrification of multistage anoxic and oxic biofilm (MAOB) process in three tanks using facultative denitrifying bacteria inoculum was developed to simultaneously achieve desirable effluent nitrogen and organics at different hydraulic retention time (HRT) and carbon to nitrogen (C/N) mass ratios. The optimum condition was recommended as a C/N ratio of 1.5 and a HRT of A (24 h)/O (12-24 h) to achieve > 90% of nitrogen and organics removal as well as no significant variation of sulfate. The denitrifying biofilm in various tanks was dominant by Hyphomicrobium (8.9%-25.7%), Methylophaga (18.6%-25.8%) and Azoarcus (3.3%-19.6%), etc., containing > 20% aerobic denitrifiers. This explained that oxic zone in MAOB process also exhibited simultaneous nitrogen and organics removal.

Improving denitrification performance of biofilm technology with salt-tolerant denitrifying bacteria agent for treating high-strength nitrate and sulfate wastewater from lab-scale to pilot-scale.

This study focused on the application of salt-tolerant denitrifying bacteria (DBA) in an optimized biofilm process to treat high sulfate-nitrate wastewater from lab-scale to pilot-scale. Lab-scale results demonstrated the salinity, DBA inoculum, supplementary carbon and phosphorus source significantly varied the startup periods at the range of 36-74 d, and the optimum initial start-up conditions were as follows: >0.6 g/L of DBA, 2-4 of C/N ratio, 0.3-0.6 mg/L of phosphorus and a salinity-gradient domestication method. A pilot scale of biofilm technology with DBA was further developed for treating real wastewater from the desulfuration and denitration with both high nitrate (≈200 mg/L) and sulfate (2.7%). The denitrification efficiency reached above 90% after one-month gradient-salinity of 0.5%-2.7%. Mature biofilm had dominant genera Hyphomicrobium (31.80%-61.35%), Methylotenera (0.85%-20.21%) and Thauera (1.42%-8.40%), etc. Notably, the largest genera Hyphomicrobium covered the complete denitrification genes.

Microbial communities and sediment nitrogen cycle in a coastal eutrophic lake with salinity and nutrients shifted by seawater intrusion.

Coastal waters are often influenced by seawater intrusion and terrestrial emissions because of its special location. In this study, the dynamics of microbial community with the role of nitrogen cycle in sediment in a coastal eutrophic lake were studied under a warm season. The water salinity gradually increased from 0.9‰ in June to 4.2‰ in July and 10.5‰ in August because of seawater invasion. Bacterial diversity of surface water was positively related with salinity and nutrients of total nitrogen (TN) as well as total phosphorus (TP), but eukaryotic diversity had no relationship with salinity. In surface water, algae belonging to Cyanobacteria and Chlorophyta were dominant phyla in June with the relative abundances of >60%, but Proteobacteria became the largest bacterial phylum in August. The variation of these predominant microbes had strong relationship with salinity and TN. In sediment, the bacterial and eukaryotic diversity was greater than that of water, and a significantly different microbial community was observed with dominant bacterial phyla Proteobacteria and Chloroflexi, and dominant eukaryotic phyla Bacillariophyta, Arthropoda, and Chlorophyta. Proteobacteria was the only enhanced phylum in the sediment with the highest relative abundance of 54.62% ± 8.34% due to seawater invasion. Denitrifying genera (29.60%-41.81%) were dominant in surface sediment, then followed by microbes related to nitrogen fixation (24.09%-28.87%), assimilatory nitrogen reduction (13.54%-19.17%), dissimilatory nitrite reduction to ammonium (DNRA, 6.49%-10.51%) and ammonification (3.07%-3.71%). Higher salinity caused by seawater invasion enhanced the accumulation of genes involved in dentrificaiton, DNRA and ammonification, but decreased genes related to nitrogen fixation and assimilatory nitrogen reduction. Significant variation of dominant genes of narG, nirS, nrfA, ureC, nifA and nirB mainly caused by the changes in Proteobacteria and Chloroflexi. The discovery of this study would be helpful to understand the variation of microbial community and nitrogen cycle in coastal lake under seawater intrusion.

Enhanced removal of mixed VOCs with different hydrophobicities by Tween 20 in a biotrickling filter: Kinetic analysis and biofilm characteristics.

Mass transfer limitation usually causes the poor performance of biotrickling filters (BTFs) for the treatment of hydrophobic volatile organic compounds (VOCs) during long-term operation. In this study, two identical lab-scale BTFs were established to remove a mixture of n-hexane and dichloromethane (DCM) gases using non-ionic surfactant Tween 20 by Pseudomonas mendocina NX-1 and Methylobacterium rhodesianum H13. A low pressure drop (≤110 Pa) and a rapid biomass accumulation (17.1 mg g-1) were observed in the presence of Tween 20 during the startup period (30 d). The removal efficiency (RE) of n-hexane was enhanced by 15.0%- 20.5% while DCM was completely removed with the inlet concentration (IC) of 300 mg·m-3 at different empty bed residence times in the Tween 20 added BTF. The viable cells and the relative hydrophobicity of the biofilm were increased under the action of Tween 20, which facilitated the mass transfer and enhanced the metabolic utilization of pollutants by microbes. Besides, Tween 20 addition enhanced the biofilm formation processes including the increased extracellular polymeric substance (EPS) secretion, biofilm roughness and biofilm adhesion. The kinetic model simulated the removal performance of the BTF with Tween 20 for the mixed hydrophobic VOCs, and the goodness-of-fit was above 0.9.

Antibiotics resistance evolution of isolated Vibrio parahaemolyticus from mariculture under the continuous culture of sub-inhibitory concentrations of Ulva fasciata hydroponic solution.

The outbreak of vibriosis from Vibrio (V.) parahaemolyticus is widespread in the mariculture, and live macroalgae has been considered to be effective and eco-friendly approach for the control of vibriosis. Three V. parahaemolyticus strains with ß-lactam antibiotics resistance (resistant to ampicillin (AM), amoxicillin (AMX)) were isolated from mariculture in study, and the antibiotics resistance evolution mechanism was examined at the sub-inhibitory concentration (SIC) of hydroponic solution of Ulva (U.) fasciata (HSUF). The HSUF with the highest density (20 g fresh weight U. fasciata L-1) demonstrated the strongest inhibitory rates (47.0 %-65.8 %) on the three strains during the stable phase (8-24 h) of growth curve, which indicated that the HSUF (≤20 g L-1) could be considered to be at SIC for V. parahaemolyticus strains. After continuous subculture of V. parahaemolyticus with three dilutes (1/2 (HT), 1/20 (MT) and 1/50 (LT)) of HSUF (20 g L-1), all the strains of 20th generation were still resistant to AM and AMX. However, the LT condition reduced MIC of AM (2-16 times) and AMX (0-2 times) to strains, while MT and HT showed significantly various effect of ß-lactam antibiotics resistance on different strains. The biofilm formation and ROS content of V. parahaemolyticus were almost positively correlated to the concentrations of HSUF. Transcriptome sequencing analysis of a representative strain showed that the lower concentrations of HSUF caused more down-regulated DEGs of the strains, and more down-regulated (vmeA, vmeB, sapA, mrdA) DEGs of strains were related to the pathway of ß-lactam antibiotics resistance at LT condition. Thus, low concentration of HSUF was seemed to have better improvement for V. parahaemolyticus strains resistant to ß-lactam antibiotics, which were mainly related to the impairment of biofilm formation, ROS and efflux pump.

Interaction of tetrahydrofuran and methyl tert-butyl ether in waste gas treatment by a biotrickling filter bioaugmented with Piscinibacter caeni MQ-18 and Pseudomonas oleovorans DT4.

Bioaugmented biotrickling filter (BTF) seeded with Piscinibacter caeni MQ-18, Pseudomonas oleovorans DT4, and activated sludge was established to investigate the treatment performance and biodegradation kinetics of the gaseous mixtures of tetrahydrofuran (THF) and methyl tert-butyl ether (MTBE). Experimental results showed an enhanced startup performance with a startup period of 9 d in bioaugmented BTF (25 d in control BTF seeded with activated sludge). The interaction parameter I2,1 of control (7.462) and bioaugmented BTF (3.267) obtained by the elimination capacity-sum kinetics with interaction parameter (EC-SKIP) model indicated that THF has a stronger inhibition of MTBE biodegradation in the control BTF than in the bioaugmented BTF. Similarly, the self-inhibition EC-SKIP model quantified the positive effects of MTBE on THF biodegradation, as well as the negative effects of THF on MTBE biodegradation and the self-inhibition of MTBE and THF. Metabolic intermediate analysis, real-time quantitative polymerase chain reaction, biofilm-biomass determination, and high-throughput sequencing revealed the possible mechanism of the enhanced treatment performance and biodegradation interactions of MTBE and THF.

Characteristics of exopolysaccharides produced by isolates from natural bioflocculant of Ruditapes philippinarum conglutination mud.

Three novel types of exopolysaccharides (EPS) EPS-S8, EPS-S5, and EPS-F10 were extracted and purified from bacterial isolates Bacillus sp. GHS8, Pseudoalteromonas sp. GHS5 and Psychrobacter sp. GHF10, which were originated from natural bioflocculant of Ruditapes philippinarum conglutination mud (RPM), respectively. The EPS had similar function groups C-H, N-H, C-O, and C = O. The EPS were composed of different monosaccharides (EPS-F10, Man: GlcN: GlcUA: GalUA = 1:0.66:5.75:0.51; EPS-S5, Man: Gal: GlcN: Rib = 1: 0.50: 2.94: 0.26; EPS-S8, Man: Gal: GlcN = 1:1.54:7.69). The molecular weights (Mw) of EPS were ordered as 51.4 kDa (EPS-S5) > 9.15 kDa (EPS-S8) > 4.41 kDa (EPS-F10). Three types of EPS all showed higher peak flocculation activities than the reported crude EPS from the RPM. Besides, the EPS also exhibited efficient decoloration and antioxidation activities, especially for EPS-S8, which might be due to the low Mw and specific monosaccharide composition.

Efficient anaerobic bioremediation of high-concentration benzo[a]pyrene in marine environments.

Benzo[a]pyrene (BaP), a persistent organic pollutant that may accumulate in sea sediments after oil spill or BaP chemical leakage accidents, considerably harms marine ecosystems and human health. Previous studies have been predominantly focused on its degradation at low concentrations, while the remediation of BaP pollution with high concentrations was neglected. Additionally, the metabolic pathways associated with its anaerobic degradation remain unclear. As a first attempt, super-efficient systems for BaP anaerobic degradation were established, and the corresponding metabolic pathways were elucidated in this study. The results showed that the BaP removal rate in BaP-only system with initial concentrations of 200 mg/L reached 3.09 mg/(L·d) within 45 days. Co-solvent, acetone promoted anaerobic BaP degradation (4.252 mg/(L·d)), while dichloromethane showed a newly-discovered co-metabolic effect. In the system with 500 mg/L of BaP and dichloromethane addition, the removal rate increased drastically (14.64 mg/(L·d)) at 400 mg/L turn point of BaP. Additionally, the corresponding microbial community-level metabolic network was firstly proposed.

Anaerobic degradation of high-concentration polycyclic aromatic hydrocarbons (PAHs) in seawater sediments.

Recurring oil spill accidents have been a global challenge and contribute to PAHs' heavy accumulation in marine sediments. The rapid bioremediation of PAHs with high concentrations in marine sediments has rarely been studied. In this study, four representative PAHs in crude oil were tested for fast anaerobic biodegradation. An efficient system for the anaerobic degradation of high-concentration PAHs was obtained using petroleum-acclimated marine sediments as inoculants in the treatment system. The degradation efficiencies of benzo[b]fluoranthene, benzo[a]pyrene, pyrene, and phenanthrene reached 0.21, 1.71, 3.89, and 4.10 mg/(L·d), respectively, which are 16, 2.8, 1.8, and 1.0 times higher than the reported values. Nitrate was preferred to sulfate as an electron acceptor. The acclimated sediment contains a high abundance of hydrocarbon-degrading bacteria. The number and diversity of species in the treatment system supplemented with PAHs decreased, but the abundance of some hydrocarbon-degrading bacteria and hydrocarbon-intermediate utilising bacteria increased, and ecological succession was observed.

The role of Ulva fasciata in the evolution of the microbial community and antibiotic resistance genes in maricultural sediments.

This study explored changes in the microbial community and antibiotic resistance genes (ARGs) in maricultural clam sediment after 3-month co-culture with different densities (0, 5 and 12 g L-1) of seaweed Ulva fasciata (U. fasciata). The maximum removal rates of NO3--N, PO43--P, and inhibition of Vibrio culturability occurred at presence of 12 g L-1U. fasciata. A significant decrease by 14.0% of the total ARGs was found in control sediment without U. fasciata after separation from the original niches, while the total ARGs further increased by 5.58%and 4.65% at presence of 5 and 12 g L-1 of U. fasciata in compared with control sediment, respectively, strongly related with Chloroflexi, Spirochaetes, Proteobacteria and Bacteroidetes hosts. In addition, U. fasciata favored the decline of absolute gene numbers of some tetracycline resistance genes (tetPB, tetW, otrA, tetT, tetO) and class 1 integron-integrase gene.

Dynamics of denitrification performance and denitrifying community under high-dose acute oxytetracycline exposure and various biorecovery strategies in polycaprolactone-supported solid-phase denitrification.

Solid-phase denitrification (SPD) is a promising technology for nitrate-rich water purification. This study aimed to examine the variation in denitrification performance and denitrifying community under high-dose acute oxytetracycline (OTC) exposure and various biorecovery strategies. The denitrification performance was impaired significantly after one-day OTC shock at 50 mg L-1 in a continuous-flow SPD system supported by a polycaprolactone (PCL) carrier but could rapidly recover without the addition of OTC. When 50 mg L-1 OTC stress was applied for a longer time in the batch tests, a natural recovery period of more than 20 days was required to reach more than 95% nitrate reduction. Under the same conditions, the addition of both mature biofilm-attached PCL carrier and fresh biofilm-free PCL carrier significantly shortened the recovery time for efficient nitrate reduction, mainly due to the increase in organic availability from the PCL carriers. However, the composition of the microbial community notably changed due to the effects of OTC according to high-throughput sequencing and metagenomic analysis. Genes encoding NAR and NIR were much more sensitive than those encoding NOR and NOS to OTC shock. Tetracycline resistance gene (TRG) enrichment was 15.86% higher in the biofilm that experienced short-term OTC shock than in the control biofilm in the continuous-flow SPD system.

Comparative analysis of denitrification performance, denitrifying community and functional genes to oxytetracycline exposure between single and hybrid biodegradable polymers supported solid-phase denitrification systems.

Biodegradable carrier are vital for the solid-phase denitrification (SPD) systems for treating nitrate-rich water. Two solid-phase denitrification reactors were developed with both 200 g L-1 of single (polycaprolactone, PCL) (R1) and hybrid solid carbon sources (PCL/polylactic acid (PLA) /polyhydroxyalkanoates (PHA)) (R2) to examine the denitrification performance, denitrifying community and functional genes to various oxytetracycline (OTC) exposure in this study, respectively. Complete denitrification performance was achieved in the both SPD systems at low stress of OTC (1 mg L-1), but then dramatically reduced to less than 20% of nitrate reduction efficiency after one-month high OTC stress (10 mg L-1), and rapidly recovered to stable nitrate removal rates of 76.77 ± 5.48% (R1) and 40.68 ± 4.40% (R2) after the next day of no OTC stress. However, the reactor R1 with single PCL carriers acquired more efficient nitrate removal rate than that of reactor R2 at the high OTC stress and recovery phase with OTC stress, mainly due to the more organics availability from the single PCL carriers. The richness and diversity of nirK and nirS deintrifiers significantly declined at high OTC stress, and much more of those occurred in biofilm R1 with more organics availability. Besides, biofilm R1 achieved much more abundant periplasmic nitrate reductase, nitrite reductase genes and tetracycline resistance genes after high OTC stress, which explained the potential resistance to OTC and rapid recovery efficiency after no stress of OTC. Thus, the organics availability played an important role in assuring SPD system to be efficient under high OTC stress.

Variation in microbial populations and antibiotic resistance genes in mariculture sediments in the present of the seaweed Ulva fasciata and under selective pressure of oxytetracycline.

The widely distributed seaweed Ulva fasciata has nutrient absorption abilities and can be used in the bioremediation of polluted maricultural environments. This study explored microbial community and antibiotic resistance gene (ARG) variation in mariculture sediments in response to different trace levels (10, 100, and 500 µg L-1) of oxytetracycline (OTC) and the presence of Ulva fasciata. The increase in OTC level promoted nutrient (NO3_-N and PO43--P) removal mainly due to Ulva fasciata adsorption. The abundances of the Euryarchaeota and Planctomycetes phyla in sediments were positively related to the increase in OTC stress, while a negative correlation occurred for the Proteobacteria phylum via metagenomic analysis. Compared with the control system, the increase rates of total ARGs were 3.90%, 7.36% and 13.42% at the OTC levels of 10, 100 and 500 µg L-1, respectively. OTC stress mainly favoured the collateral enrichment of non-corresponding polypeptide and MLS ARGs, mainly due to the enrichment of the phyla Planctomycetes and Euryarchaeota by the synergistic effect of OTC and nutrients. The results of quantitative PCR with tetracycline resistance genes (TRGs) (tetO, tetT, tetPB, tetW and otrA) and a horizontal transfer gene (intl1) demonstrated that all of genes had much higher gene numbers in sediments after 3 months of OTC stress than in those without OTC stress, which was strongly related to the variation in the phyla Bacteroidetes, Gemmatimonadetes and Acidobacteria. The significant correlation between intl1 and the target TRGs is indicative of the important role of the horizontal transfer of integron-resistant genes in the spread of TRGs.

Performance, kinetics characteristics and enhancement mechanisms in anammox process under Fe(II) enhanced conditions.

In order to explore the performance, kinetics characteristics and enhancement mechanisms in anammox process under ferrous iron enhanced conditions, a laboratory-scale UASB anammox reactor has been built up and operated for 534 days. Experimental results showed that the Anammox process was successfully started up in a short operation period and the TNRE reached 83.34 ± 2.96% with a maximum total nitrogen removal rate of 14.4 kg m-3 d-1 after long-term operated under influent Fe(II) concentration of 5.3 mg L-1. Simulation results using different kinetic models showed that the Stover-Kincannon model and the Grau second-order model were useful for describing the anammox performance under Fe(II) enhanced conditions. Extracellular polymeric substance (EPS) act a pivotal part in the granulation of Anammox sludge and the improvement of anammox activity. Iron improved the hydrophobicity of the sludge by reducing the PN/PS ratios, and also increased the Anammox granular diameter. The granular diameter of higher than 2.00 accounted for 58.3% of the total sludge. At the same time, the presence of iron decreased EPS levels, and also decreased the iron adsorption ability to sludge. More iron was transported into Anammox, which improved the nitrogen removal ability in the Anammox reactor.

Response of denitrifying community, denitrification genes and antibiotic resistance genes to oxytetracycline stress in polycaprolactone supported solid-phase denitrification reactor.

The coexistence of nitrate and antibiotics in wastewater is a common problem. The study aimed to explore the response of denitrifying community, denitrification genes and antibiotic resistance genes (ARGs) to oxytetracycline (OTC) stress in polycaprolactone (PCL) supported solid-phase denitrification (SPD) reactors. Complete nitrate reduction (greater than99%) was achieved in SPD system with OTC stress of 0, 0.05, 0.25 and 1 mg L-1 during three-month operation, while it significantly declined by about 5% at a further increased OTC level of 5 mg L-1. The efficient denitrification strongly related with a rich diversity of denitrifiers, while the abundances of which dramatically reduced as the OTC concentration reached ≥0.25 mg L-1, which caused significant decline of denitrification genes, especially for narH, narJ, narI nirD, nosZ, and norB. Tetracycline resistance genes were a major type of promoted ARGs by different OTC stress, mainly related with the increase of tet36, tetG, tetA, tetM and tetC.

Saccharospirillum alexandrii sp. nov., isolated from the toxigenic marine dinoflagellate Alexandrium catenella LZT09.

A Gram-stain-negative, strictly aerobic, non-motile and non-pigmented spirillum, designated strain LZ-5T, was isolated from cultures of the paralytic shellfish poisoning (PSP) toxin-producing marine dinoflagellate Alexandrium catenella LZT09 collected from the Zhoushan sea area in the East China Sea during an algal bloom. The isolate grew at 4-40 °C (optimum, 25-33 °C) and pH 5.0-9.0 (optimum, 7.5) in the presence of 0.5-10 % (w/v) NaCl (optimum, 4.0 %). Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain LZ-5T clearly belonged to the genus Saccharospirillum of the family Saccharospirillaceae. Strain LZ-5T shared highest 16S rRNA gene sequence similarity with Saccharospirillum impatiens EL-105T (98.9 %), Saccharospirillum mangrovi HK-33T (97.2 %), Saccharospirillum correiae CPA1T (96.8 %), Saccharospirillum salsuginis YIM-Y25T (96.8 %) and Saccharospirillum aestuarii IMCC 4453T (95.1 %). The average nucleotide identity and in silico DNA-DNA hybridization between strain LZ-5T and the two most closely related Saccharospirillum strains, S. impatiens EL-105T and S. mangrovi HK-33T, were 82.2 and 19.3 %, and 72.2 and 13.2 %, respectively. The predominant respiratory quinone of strain LZ-5T was Q-8, and the major fatty acids were summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c), summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) and C16 : 0. The polar lipids of strain LZ-5T were diphosphatidylglycerol (DPG), phosphatidylethanolamine (PE), phosphatidylcholine (PC), glycolipid (GL), two unidentified glycophospholipids (GPLs), three unidentified aminophospholipids (APLs) and two unidentified lipids. The genomic DNA G+C content was 57.2 mol%. On the basis of this polyphasic characterization, strain LZ-5T represents a novel species of the genus Saccharospirillum, for which the name Saccharospirillum alexandrii sp. nov. is proposed. The type strain is LZ-5T (=KCTC 62460T=CCTCC AB2017232T).

Microbial origin of bioflocculation components within a promising natural bioflocculant resource of Ruditapes philippinarum conglutination mud from an aquaculture farm in Zhoushan, China.

Ruditapes philippinarum conglutination mud (RPM) is a byproduct from the aquiculture of an important commercially bivalve mollusk R. philippinarum and has been recently reported as a promising natural bioflocculant resource. However the origin of bioflocculation components within RPM is still a pending doubt and impedes its effective exploitation. This study investigated the probability that RPM bioflocculation components originate from its associated microbes. RPM samples from an aquaculture farm in Zhoushan of China were applied to characterize its microbial community structure, screen associated bioflocculant-producing strains, and explore the homology between extracellular polysaccharides (EPS) from bioflocculant-producing isolates and RPM flocculation components. Results showed that RPM exhibited high bacterial biodiversity, with Proteobacteria, Bacteroidetes and Actinobacteria as the most abundant phyla; hgcI_clade, CL500_29_marine_group, Fusibacter, MWH_UniP1_aquatic_group and Arcobacter as the dominant genera. Fourteen highly efficient bioflocculant-producing strains were screened and phylogenetically identified as Pseudoalteromonas sp. (5), Psychrobacter sp. (3), Halomonas sp. (2), Albirhodobacter sp. (1), Celeribacter sp. (1), Kocuria sp. (1) and Bacillus sp. (1), all of which except Bacillus sp. were reported for the first time for their excellent flocculation capability. Furthermore, EPS from the bioflocculant-producing strains exhibited highly similar monosaccharide composition to the reported flocculation-effective RPM polysaccharides. On the other hand, the existence of fungi in RPM was rare and showed no flocculation functionality. Findings from Zhoushan RPM strongly supported that RPM flocculation components were of bacterial origin and make RPM reproduction possible by fermentation approach.