Neomicrocoleus gen.nov.(Microcoleaceae,Oscillatoriales),a novel cyanobacterial genus from benthic mats in a water channel

A new filamentous cyanobacterial strain(CHAB 4127)was successfully isolated from the algal mat during the field investigation of the open channel from Luanhe River to Tianjin,China.The polyphasic approach combining morphological,ultrastructural,ecological,and molecular features was used to characterize this studied strain.The strain is morphologically similar to the Microcoleus-like cyanobacterial taxa under light microscopy,and the radial arrangement of thylakoids is also consistent with that of Microcoleus-like groups.The phylogenetic position of CHAB 4127 based on 16S rRNA gene sequences,is shown to be clearly clustered into an independent clade with the newly established genus Microcoleusiopsis.The maximum similarity of 16S r RNA gene of the studied strain with other existing related cyanobacterial taxa is 93.97%,and the ITS secondary structures is also obviously different from other members of Microcoleaceae.Based on all the above evidence,we proposed the establishment of this novel cyanobacterial genus as Neomicrocoleus,with its type species,Neomicrocoleus tianjinensis.

Relationship between morphospecies and microcystin-producing genotypes of Microcystis species in Chinese freshwaters

Twenty water bodies in China were sampled,and 186 strains of different Microcystis species were isolated,from which eight morpho species were identified and 43 stains containing the mcyB gene were detected.Phylogenetic analysis based on the mcyB gene indicated that the microcystin(MC)-producing Microcystis in China could be divided into two groups(ⅠandⅡ)and showed significant differences between the two groups.The maximum sequence similarity was 69.1%.Microcystins(MCs)were measured by high-performance liquid chromatography(HPLC)analysis,and no microcystin-RR(MC-RR)was detected in some strains belonging to GroupⅡ.Compared to other regions of the world,the proportion of Chinese MC-producing was different,and the regional differences were more obvious.A whole-cell polymerase chain reactio(PCR)assay was conducted to analyze the proportion of the mcyB gene in the laboratory cultured and field cultured Microcystis.The proportion of four morphospecies(M.vividis,M.ichthyoblabe,M.novacekii,and M.aeruginosa)that contained the mcyB gene exceeded 50%in the field cultured sample s.Compared with former studies,M.aeruginosa was the mo st likely morphotype that can produce MCs in the world.This study provided new insight of Microcystis hazard assessment and field monitoring.

Succession of Aphanizomenon flos-aquae and Microcystis aeruginosa in direct co-culture experiments at different temperatures and biomasses

Cyanobacterial blooms have become a serious global environmental issue due to their potential risk for releasing detrimental secondary metabolites into aquatic ecosystems,posing a great threat to water quality management for public health authorities.Aphanizomenon,a common filamentous cyanobacterial genus belonging to Nostocales,is under particular concern because its several members are able to form harmful blooms.Furthermore,succession of bloom between A.flos-aquae and Microcystis occurs in many natural lakes.To evaluate the competitiveness of A.flos-aquae vs.M.aeruginosa,two sets of experiments at different ratios of biomass at 15℃and 25℃were conducted.Results show that at 15℃,the two species were able to coexist,and A.flos-aquae showed a specific higher growth rate,and its growth was promoted by the presence of M.aeruginosa.At 25℃,the growth of A.flos-aquae was inhibited by the biomass of M.aeruginosa,and M.aeruginosa suppressed A.flos-aquae in competition.Additionally,the vegetative cell size of A.flos-aquae was significantly influenced by the co-culture with M.aeruginosa,whereas the filament length of A.flos-aquae was not significantly affected.This study confirms that temperature is the dominating factor on the succession of A.flos-aquae and M.aeruginosa of a different biomass.

Description of two new species of Pseudoaliinostoc(Nostocales,Cyanobacteria)from China based on the polyphasic approach

Two cyanobacterial strains CHAB5870 and CHAB5871 morphologically identifi ed as Nostoc-like species were isolated from different habitats in China,and they were phylogenetically and taxonomically characterized based on a polyphasic approach combining morphological,ecological,and molecular data.In the 16S rRNA gene phylogeny inferred using maximum likelihood,maximum-parismony,and bayesian inference methods,these two strains clustered within the Pseudoaliinostoc clade.The 16S rRNA gene sequences of these two strains displayed≥95.5%and≤98%similarity to Pseudoaliinostoc species,which indicated them to represent new species of the genus Pseudoaliinostoc.Furthermore,the unique pattern of D1-D1′and Box-B helix of the 16S–23S rRNA internal transcribed spacer(ITS)secondary structure also revealed that two strains represented novel species.These results supported the establishment of two new Pseudoaliinostoc species with the name P.jiangxiense sp.nov.and P.yunnanense sp.nov.

First report of microcystin production in Microcystis smithii Komrek and Anagnostidis(Cyanobacteria) from a water bloom in Eastern China

A water bloom sample collected from Lake Dishui in Shanghai was characterized. The morphological identification showed that Micorcystis wesenbergii and Micorcystis smithii were the main component of the bloom. Five strains of M. smithii were successfully isolated. Their 16S rRNA gene sequences based phylogenetic tree showed that the five strains of M. smithii intermixed with strains of other morphospecies in Microcystis. A fragment of mcy gene encoding for microcystin synthetase was detected in one of the five M. smithii strains （CHAB 2183）, indicating its potential of microcystin production. High performance liquid chromatography analysis confirmed M. smithii CHAB 2183 to produce microcystin-RR as 1550 μg per gram dry weight cells. The present investigation, for the first time, reported the isolated strains of M. smithii and microcystin production from M. smithii.

Responses of Synechocystis sp. PCC 6803 (cyanobacterium) photosystem Ⅱ to pyrene stress

In order to explore the mechanism of acute toxicity for pyrene to cyanobacterial organisms, the responses of Synechocystis sp. PCC 6803 photosystem Ⅱ （PS Ⅱ） under pyrene stress were studied. The results showed there was no significant difference about the oxygen evolution under 0.125 mg/L pyrene stress when compared with control, but it was significantly lower than control at 0.625 mg/L pyrene. Polyphasic chlorophyll-a fluorescence transients in cells of Synechocystis sp. PCC 6803 exhibited a typical increase including O, J, I, and P phases. Fluorescence yield at phases J, I and P declined slightly at 0.125 and 0.625 mg/L pyrene, and significantly lower than control at 3.125 mg/L. According to the parameters deviated from JIP-test, no modification was induced by pyrene both at the donor side and at the acceptor side of PS Ⅱ, and the reaction centre of PS Ⅱ is the primary damaging target. Based on the expressing of four key genes （psbA, psbB, psbC and psbO） of PS Ⅱ, only psbA showed significant difference at 3.125 mg/L pyrene when compared with control.