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Growth of nutrient‐replete Microcystis PCC 7806 cultures is inhibited by an extracellular signal produced by chlorotic cultures
Author(s) -
Dagnino Denise,
De Abreu Meireles Diogo,
De Aquino Almeida João Carlos
Publication year - 2006
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/j.1462-2920.2005.00866.x
Subject(s) - biology , microcystis , extracellular , population , nutrient , cyanobacteria , botany , growth medium , cell culture , microbiology and biotechnology , biochemistry , bacteria , ecology , genetics , demography , sociology
Summary The frequency of cyanobacterial blooms has been increasing all over the world. These blooms are often toxic and have become a serious health problem. The aim of this work was to search for population density control mechanisms that could inhibit the proliferation of the toxic bloom‐forming genus Microcystis. Microcystis PCC 7806 cultured for long periods in liquid ASM‐1 medium loses its characteristic green colour. When a medium of chlorotic cultures is added to a nutrient‐replete culture, cell density increase is drastically reduced when compared with controls. Inhibition of cell proliferation occurs in Microcystis cultures from any growth stage and was not strain‐specific, but other genera tested showed no response. Investigations on the mechanism of growth inhibition showed that cultures treated with the conditioned medium acquired a pale colour, with pigment concentration similar to that found in chlorotic cultures. Ultrastructural examination showed that the conditioned medium induced thylakoid membrane disorganization, typical of chlorotic cells, in nutrient‐replete cultures. An active extract was obtained and investigations showed that activity was retained after heating and after addition of an apolar solvent. This indicates that activity of the conditioned medium from chlorotic cells results from non‐protein, apolar compound(s).