Electron Microscopic Study on Lysis of a Cyanobacterium Microcystis

Abstract

In a previous study, it was suggested that β-cyclocitral plays an important role in understanding the lysis of cyanobacteria under natural conditions. The present study was conducted in order to understand how the β-cyclocitral lyses cyanobacterial cells, and other anticyanobacterial agents were also investigated. The preliminary study using a scanning electron microscope (SEM) demonstrated that there were three types of morphological changes in the cyanobacterial cells when they were incubated with anticyanobacterial agents: volatile compounds from cyanobacteria cause shrinking and then wrinkling; terpenoids contact directly and cause stripping; basic amino acids cause swelling and then collapsing. In order to clarify the extreme difference in the damage during the morphological changes between the β-cyclocitral and L-lysine (Lys), the transmission electron microscope (TEM) technique was applied. Although a definite difference in the morphological damage was observed, a plausible mechanism for β-cyclocitral could be not deduced. Throughout the experiments using antibiotics, it was found that the apparent morphological changes after lysis did not always correspond to the mode of action.

Kinetics of cell lysis for Microcystis aeruginosa and Nitzschia palea in the exposure to β-cyclocitral

“…1(a)-C and D and (b)-C and D). Similar SEM micrographs were obtained by Ozaki et al [22] and Lin et al [12] for Microcystis cells exposed to various algal metabolites and for the cells of M. aeruginosa after chlorination. For N. palea, cracks formed on the surface at 1.5 h (Fig.…”

“…It is the product of an oxidative cleavage reaction of ␤-carotene, catalyzed by ␤-carotene oxygenases bound on the Microcystis cell membrane under aerobic conditions [21]. Although ␤-cyclocitral has been shown to be anticyanobacterial, the studies were mostly based on color change [19], absorbance measured with a spectrophotometer, or scanning electron microscope (SEM) observation [22]. In addition, the effect of ␤-cyclocitral on other algae, such as diatoms, has not been reported.…”

Cyanobacterial Blue Color Formation during Lysis under Natural Conditions

“…In the present study, we examined the wrinkled cells using an SEM (see Fig. S3B in the supplemental material) and observed that the cell walls were broken; the resulting cytoplasm was identified using an optical microscope in the same manner as previously reported (27) (Fig. 4B).…”

“…Ozaki et al studied the morphological change in the lysed Microcystis cells after the spiking of ␤-cyclocitral using electron microscopic methods in the laboratory (27). They found that the cells initially shrank and then gradually became wrinkled when using the SEM, and damage to the cell membrane or cell wall on the surface was observed.…”

Inhibition of Microcystis aeruginosa by the Extracellular Substances from an Aeromonas sp.

“…Additionally, cells of M. aeruginosa treated with the extracellular substances were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Samples were prepared according to Ozaki et al [24] and Wang et al [27]. As shown in Fig.…”