Differences in Responses to Darkness betweenMicrocystis aeruginosaandChlorella pyrenoidosa

Abstract

The effect of darkness on the cyanobacterium Microcystis aeruginosa and the green alga Chlorella pyrenoidosa were observed. Cell growth, metabolic activity, chlorophyll a fluorescence, cell size, and maximum quantum yield (F, : F,) were determined.

Different tolerances and responses to low temperature and darkness between waterbloom forming cyanobacterium Microcystis and a green alga Scenedesmus

“…Similar result was reported by Zhang et al (2007) who found that Microcystis was more capable of withstanding the dark circumstances. Furusato et al (2004) found that the cell numbers of M. aeruginosa decreased markedly after more than 7 days of darkness and the abundance of S. quadricauda was not affected during 20 days of darkness.…”

“…However, the cell number and Chl a content of S. quadricauda decreased significantly. Similar result was also found in Chlorella pyrenodosa after darkness (Zhang et al, 2007). Compared to colonial Microcystis, the cell number of unicellular Microcystis had a significant decrease, suggesting that colonial Microcystis can survive a longer period under the stress of darkness and low temperature than unicellular Microcystis.…”

“…Jochem (1999) defined marine phytoplankton with two distinct types of metabolic response to darkness using FDA method: Type I with adaptation to stress by reducing their metabolism, and Type II with an unchanged metabolic activity. Zhang et al (2007) also indicated that freshwater phytoplankton had two distinct types of metabolic response to darkness. In the present study, two distinct types of physiological responses to darkness and low were revealed in the three strains.…”

“…Verspagen et al (2004) found that there were photochemically viable Microcystis cells in the water columns and sediments of Lake Volkerak throughout the year. Previous studies have been conducted by dealing with responses of Microcystis and other phytoplankton to only one factor of darkness or low temperature (Dehning & Tilzer, 1989;Furusato et al, 2004;Chu et al, 2007;Zhang et al, 2007). However, it is well known that the sediment environment of waters in winter represent a series of unfavorable conditions such as low temperature and darkness.…”

Metabolic activity and membrane integrity changes inMicrocystis aeruginosa– new findings on hydrogen peroxide toxicity in cyanobacteria

“…Whereas some species of marine phytoplankton adapt to the dark by reducing their metabolism to a lower level of activity (type I cells), other species maintain unchanged metabolic activity (type II) (Jochem, 1999). As has been suggested by other authors (Zhang et al, 2007;Wu et al, 2008) and confirmed by our study, M. aeruginosa can be included in the former group, since its metabolic activity (measured as fluorescein fluorescence after FDA hydrolysis) decreases in darkness. The results of our study also proved that the addition of H 2 O 2 to cyanobacterial cell suspensions can inhibit metabolic activity regardless of the experimental regime.…”