Modulation of microcystin congener abundance follo

Authors: Jonathan Puddick Michèle R Prinsep Susanna A Wood S Craig Cary David P Hamilton

Publish Date: 2016/03/07

Volume: 50, Issue: 2, Pages: 235-246

PDF Link

Abstract

Microcystins are a group of cyclic peptides which are commonly produced by freshwater cyanobacteria and are harmful to humans and other animals when ingested As the toxicity of microcystins varies according to their structure it is important to understand the environmental variables which influence microcystin congener abundance Because of the differential levels of nitrogen in amino acids incorporated into microcystins nitrogen concentration might play an important role During this study Microcystis CAWBG11 was grown in batch culture until nitrogendeplete Over the duration of the study the relative abundance of the microcystin congeners present shifted The relative abundance of the argininecontaining microcystins decreased whilst the congeners which did not contain arginine increased These changes coincided with a large decrease in nitrate concentration to 035  of initial levels Linear regression of log10 microcystin content and nitrate concentration revealed slopes which were dependent upon the number of arginine residues present in the toxin This modulation in microcystin congener relative abundance was likely to be due to scarcity of the nitrogenrich arginine during periods of nitrogen limitation During the experimental period the relative abundance of congeners with a single arginine residue at position2 did not change p  005 whilst the relative abundance of the congeners with a position4 arginine decreased significantly p ≤ 0001 Our results suggested that there arginine in the microcystin structure may be selectively modulated Furthermore the relative toxicity of the nitrogendepleted culture was found to be reduced 15  lower compared with the starting cultureWe thank Wendy Jackson Colin Monk and Lynne Parker University of Waikato New Zealand for their valued technical assistance Javier Atalah Cawthron Institute for statistical advice and the anonymous peerreviewers for their comments which have improved this paperThis research was supported by the New Zealand Ministry of Business Innovation and Employment UOWX1503 Enhancing the health and resilience of New Zealand lakes the Marsden Fund of the Royal Society of New Zealand 12UOW087 Toxic in Crowds and through a University of Waikato Doctoral Scholarship to Jonathan Puddick

Keywords: