γ-Lindane Increases Microcystin Synthesis in Microcystis aeruginosa PCC7806

Abstract

HCH factories, and the waste dumpsites associated to its production, have become a global environmental concern, and their runoff could pollute ground and surface waters with high levels of the pollutant. In this study, the influence of lindane (γ-HCH) on microcystin production has been investigated in Microcystis aeruginosa PCC7806. This toxic cyanobacterium is highly tolerant to γ-lindane (20 mg/L), and produces more toxin (microcystin) in the presence of the pollutant. Microcystis degrades γ-lindane and presence of γ-lindane induces genes involved in its own degradation (nirA). RT-PCRsq has been used to monitor changes in levels of transcripts encoded by the mcy operon (mcyD, mcyH and mcyJ), responsible for the microcystin synthesis machinery, as well as other genes involved in its transcriptional regulation, such as ntcA and fur family members. The presence of lindane in the culture media induces mcyD expression, as well as ntcA gene transcription, while other genes, such as mcyH, (putative ABC transporter), are downregulated. The amount of microcystin found in the cells and the culture media is higher when M. aeruginosa is treated with γ-lindane than in control cells. The results suggest that in a lindane polluted environment, Microcystis toxic strains may enhance their microcystin synthesis.

Relationship between Photosynthetic Capacity and Microcystin Production in Toxic Microcystis Aeruginosa under Different Iron Regimes

“…Besides, at the genetic level, MCs are synthesized by MC synthetase, which is encoded by the mcy gene cluster, and the expressions of which are often considered as an energy consumption process [ 41 , 84 ]. Interestingly, adenine triphosphate (ATP) production is one of the most important processes in cyanobacteria photosynthesis and is responsible for the energy production in cells [ 68 ].…”

Bioelectrochemical and Conventional Bioremediation of Environmental Pollutants

“…Interestingly, certain pesticides can up-regulate microcystins. In controlled studies, the organochloride lindane enhanced production of microcystin by M. aeruginosa [25]. The precise mechanism by which this can occur is not yet understood.…”

“…Some plants have been shown to accumulate cyanobacterial toxins [26]. This suggests ways in which waterways and even entire urban communities located downstream of agricultural production regions may be adversely affected by cocontamination of pesticides plus nutrient run-off [25]. Aside from large agricultural producers, individual homes and businesses also contribute to herbicide pollution run-off associated with lawn care, particularly in highly populated regions with extensive paving or other forms of impervious ground cover.…”

Contributions on Lindane Degradation by Microcystis aeruginosa PCC 7806

“…Cyanobacteria are able to tolerate and even metabolize moderate doses of organochlorine pesticides, such as lindane (γ-hexachlorocyclohexane) [1][2][3][4][5], one of the most persistent and widely used in recent decades. Previous work showed that Microcystis aeruginosa PCC 7806 degrades lindane, and that in the presence of lindane, microcystin synthesis is enhanced [6] and oxidative stress responses are induced [6]. However, there is not yet information concerning the degradative pathway in cyanobacteria.…”

“…Cyanobacteria are a good candidate to bioremediate HCH from surface waters, due to its photoautotrophic growth, plasticity, and ability to survive in a wide range of environmental conditions. Previous work suggested the presence of potential metabolic machinery to degrade HCH [1][2][3][4][5][6], which makes cyanobacteria a good candidate for the bioremediation of lindane in polluted aquatic ecosystems.…”