title: Temporal variations in microcystin-producing cells and microcystin concentrations in two fresh water ponds.
abstract: The relationship between microcystin production, microcystin-producing cyanobacteria, including Microcystis spp., and various biological and physicochemical parameters in Sankuldhara and Lakshmikund, situated in the same geographical area was studied over a period of 1.5 years. Seasonal variation in cyanobacterial 16S rRNA, Microcystis spp. 16S rRNA, mcyA and mcyB genes were quantitatively determined by real-time PCR. Microcystis was the dominant microcystin producer in both study sites constituting 67% and 97% of the total microcystin-producing cyanobacteria at Sankuldhara and Lakshmikund, respectively. Microcystin concentrations were 2.19-39.60 μg/L and 15.22-128.14 μg/L at Sankuldhara and Lakshmikund, respectively, as determined by LC-MS. Principal component analysis revealed a strong positive correlation between microcystin concentration and the copy number of mcyA and mcyB, chlorophyll a and cyanobacterial biomass at both sites. The higher microcystin concentrations in Lakshmikund pond were attributed to the high copy number of mcy genes present coupled with the pond's eutrophication status, as indicated by high total algal biomass, high chlorophyll a content, high nutrient load and low DO. Therefore, a significant difference in microcystin concentrations, correlating with these various biological and physicochemical parameters, confirms the importance of local environmental variables in the overall regulation of microcystins production.
authors.affiliation: Centre of Advanced Study in Botany, Banaras Hindu University, Varanasi 221005, India; School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Shweta
authors.initials: S
authors.lastname: Singh
authors.affiliation: Centre of Advanced Study in Botany, Banaras Hindu University, Varanasi 221005, India.
authors.forename: Pankaj Kumar
authors.initials: PK
authors.lastname: Rai
authors.affiliation: School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Rocky
authors.initials: R
authors.lastname: Chau
authors.affiliation: Occular Biochemistry, All India Institute of Medical Sciences, New Delhi 110029, India.
authors.forename: Alok Kumar
authors.initials: AK
authors.lastname: Ravi
authors.affiliation: School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Brett A
authors.initials: BA
authors.lastname: Neilan
authors.affiliation: Centre of Advanced Study in Botany, Banaras Hindu University, Varanasi 221005, India. Electronic address: asthana.ravi@gmail.com.
authors.forename: Ravi Kumar
authors.initials: RK
authors.lastname: Asthana
mesh_terms: D052998:Microcystins / Q000096:biosynthesis*; D046931:Microcystis / Q000378:metabolism*; D061005:Ponds / Q000382:microbiology*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D012015:Reference Standards; D013997:Time Factors
chemical_list: D052998:Microcystins; D012336:RNA, Ribosomal, 16S; C078588:microcystin
keywords: 16S rRNA; Microcystin; Microcystis spp; mcyA; mcyB