Whole genome sequencing data of the submerged macrophytes growth promoting and aerobic denitrifying bacterium Bacillus velezensis NBNZ-0060.

The Bacillus velezensis strain NBNZ-0060 was isolated from the bottom sediment samples of the lake Jin in Wuhan, China. This strain is an aerobic denitrifying bacterium and able to promote growth of submerged macrophytes. The 3,929,784 bp entire genome contains 3,781 coding sequences (CDS), 27 rRNAs, 85 tRNAs, 5 ncRNAs, with an average G + C content of 46.5%. The average nucleotide identity and digital DNA-DNA values between strain NBNZ-0060 and Bacillus velezensis NRRL B-41580T were 98.28% and 84.5%, respectively. The genome data have been deposited in NCBI with the accession number CP133277.1.

First Report of Botrytis cinerea Causing Gray Mold on Tea (Camellia sinensis) in China.

Tea (Camellia sinensis (L.) O. Kuntze) is an important economic crop cultivated in China. In March 2019, leaf blight symptoms were observed on tea trees (C. sinensis cv. Fuding-dabaicha) in Enshi City (30º02'66" S, 109º01'56" W), Hubei Province (Fig. 1A). The disease occurred on the senescent flowers and mature leaves. The average disease incidence was approximately 10% of plants in the surveyed 30 ha tea garden. Initial symptoms consisted of brown lesions, which expanded and became covered with gray mold, followed by abscission. To identify the pathogen, 20 symptomatic leaves were collected and 0.5 cm2 diseased leaf pieces were excised and surface sterilized by immersion in 1.5% sodium hypochlorite (NaOCl) for 2 min, and rinsed three times in sterilized distilled water. The leaf pieces were allowed to dry, placed on potato dextrose agar (PDA) plates, and incubated at 20°C under 12h fluorescent light. The fungus formed gray to grayish brown colonies (Fig. 1B) and produced conidia after 1 week. The isolate was purified by single spore isolation. The conidia were one-celled, ellipsoid or ovoid, almost colorless, with a size range of 5.3 to 10.24 × 5.2 to 8.1 µm (n = 50) (Fig. 1C). The sclerotia produced in culture were black, round or irregular in shape and 1.3 to 2.2 × 2.0 to 3.3 mm (average 1.8 × 2.3 mm) in size. Morphological characteristics of these isolates matched the description of Botrytis spp. (Hong et al. 2001). Representative isolate LCHM was selected for molecular identification based on DNA sequencing of the ITS region of rDNA and three nuclear protein-coding genes (G3PDH, HSP60 and RPB2) (Staats et al. 2005). BLAST analysis showed that isolate LCHM (GenBank Acc. Nos. MN448502, MN448500, MN433708 and MN448501 for ITS, G3PDH, HSP60 and RPB2, respectively) shared 99 to 100% identity with B. cinerea (GenBank Acc. Nos. MH316147.1, MG846500.1, MG846504.1 and MG846510.1, respectively), which suggested that isolate LCHM belongs to B. cinerea. This identification was further confirmed by phylogenetic analysis based on combined DNA sequence data of G3PDH, HSP60 and RPB2 (Fig. 2). For the pathogenicity test, needle-wounded, attached leaves on 1-year-old C. sinensis cv. Fuding-dabaicha plants were inoculated with mycelial plugs (6 mm diameter from 2-day-old PDA cultures) or a conidial suspension (20 µL, 1×106 conidia/ml in half strength potato dextrose broth) of isolate LCHM on three plants per treatment (six leaves). The control treatments were also wounded, but only treated with agar plugs or half strength PDB. All inoculated plants and controls were incubated in a growth chamber (20°C, 90 ± 10% RH). Leaves inoculated with mycelial plugs, whether wounded or not, showed brown necrotic lesions around the agar plugs after 2 days (Fig. 1D, E), whereas conidial inoculations of wound sites showed necrotic lesions after 6 days (Fig. 1 F, G). Non-wounded leaves inoculated with conidia and all the control treatments remained symptomless. B. cinerea was reisolated from the inoculated leaves and isolates were morphologically similar to the original cultures. Gray mold of C. sinensis caused by B. cinerea has been recorded in Japan, Turkey, and Brazil (Hamaya 1981, Aziz and Harun 2010, Pereira and Mio, 2020). To our knowledge, this is the first report of gray mold caused by B. cinerea on C. sinensis in China. B. cinerea may cause economic losses of tea, therefore, more surveys in other tea-growing regions should be done to specifically search for this disease.

Environmental factors associated with the filamentous green algae Cladophora blooms: A mesocosm experiment in a shallow eutrophic lake.

The process of ecological restoration in eutrophic lakes, often results in the blooming of the filamentous green algae Cladophora. This consequently affects the growth of submerged plants and the restoration of vegetation. However, the blooming process of Cladophora and the environmental factors affecting their growth are poorly understood. This has become a difficult problem in the management of lakes. The study therefore focused on succession process of Cladophora blooms and their driving factors through mesocosm experiments in Caohai Lake. The results of our experiment indicated that Cladophora growth was mainly affected by water temperature, turbidity and soluble reactive phosphorus concentration of the habitat where Elodea nuttallii and Cladophora coexist. Nuisance Cladophora was mainly affected by turbidity (>19.24 NTU) when the water temperature was above 15.7 °C. With increasing Cladophora biomass and decreasing turbidity (<4.88 NTU), Cladophora biomass accumulation was mainly limited by the soluble reactive phosphorus concentration (<3.2 µg/L). Recorded turbidity range of 9.54-13.19 NTU was found to cause dramatic changes in the biomass of Cladophora. The results also showed that the outbreak of Cladophora blooms was mainly attributed to turbidity when the water temperature was appropriate in eutrophic lakes. These findings suggest that successful management efforts should strengthen the monitoring of transparency change in addition to controlling the phosphorus concentration to limit the Cladophora overgrowth on lake ecological restoration.

Harvesting Microalgae with Different Sources of Starch-Based Cationic Flocculants.

In this study, starches obtained from wheat, potato, and corn were used to synthesize cationic starches (CS), and the flocculation efficiency of these materials was tested with Chlorella pyrenoidosa and Botryococcus braunii cultures under different conditions. Our results indicated that these three CS had differing degrees of substitution following identical synthesis conditions. The various CS functioned similarly in this study, and the desired harmless flocculation efficiency was obtained at low dosages, with CS to microalgal biomass ratios of approximately 89 and 119 mg g-1 for C. pyrenoidosa and B. braunii, respectively. Impressive harmless harvesting efficiencies were obtained at lower dosages with respect to appropriate stirring time before the settling, with ratios ranging from 58 to 78 mg g-1 for C. pyrenoidosa cultures. The cost of microalgae harvesting can be cut dramatically by choosing cheaper starches prior to the synthetic CS and by applying suitable flocculation procedures.

Microbial Succession and Nitrogen Cycling in Cultured Biofilms as Affected by the Inorganic Nitrogen Availability.

Biofilms play important roles in nutrients and energy cycling in aquatic ecosystems. We hypothesized that as eutrophication could change phytoplankton community and decrease phytoplankton diversity, ambient inorganic nitrogen level will affect the microbial community and diversity of biofilms and the roles of biofilms in nutrient cycling. Biofilms were cultured using a flow incubator either with replete inorganic nitrogen (N-rep) or without exogenous inorganic nitrogen supply (N-def). The results showed that the biomass and nitrogen and phosphorous accumulation of biofilms were limited by N deficiency; however, as expected, the N-def biofilms had significantly higher microbial diversity than that of N-rep biofilms. The microbial community of biofilms shifted in composition and abundance in response to ambient inorganic nitrogen level. For example, as compared between the N-def and the N-rep biofilms, the former consisted of more diazotrophs, while the latter consisted of more denitrifying bacteria. As a result of the shift of the functional microbial community, the N concentration of N-rep medium kept decreasing, while that of N-def medium showed an increasing trend in the late stage. This indicates that biofilms can serve as the source or the sink of nitrogen in aquatic ecosystems, and it depends on the inorganic nitrogen availability.

Influence of phosphorus availability on the community structure and physiology of cultured biofilms.

Biofilms have important effects on nutrient cycling in aquatic ecosystems. However, publications about the community structure and functions under laboratory conditions are rare. This study focused on the developmental and physiological properties of cultured biofilms under various phosphorus concentrations performed in a closely controlled continuous flow incubator. The results showed that the biomass (Chl a) and photosynthesis of algae were inhibited under P-limitation conditions, while the phosphatase activity and P assimilation rate were promoted. The algal community structure of biofilms was more likely related to the colonization stage than with the phosphorus availability. Cyanobacteria were more competitive than other algae in biofilms, particularly when cultured under low P levels. A dominance shift occurred from non-filamentous algae in the early stage to filamentous algae in the mid and late stages under P concentrations of 0.01, 0.1 and 0.6 mg/L. However, the total N content, dry weight biomass and bacterial community structure of biofilms were unaffected by phosphorus availability. This may be attributed to the low respiration rate, high accumulation of extracellular polymeric substances and high alkaline phosphatase activity in biofilms when phosphorus availability was low. The bacterial community structure differed over time, while there was little difference between the four treatments, which indicated that it was mainly affected by the colonization stage of the biofilms rather than the phosphorus availability. Altogether, these results suggested that the development of biofilms was influenced by the phosphorus availability and/or the colonization stage and hence determined the role that biofilms play in the overlying water.