Light and electron microscope assessment of the lytic activity of Bacillus on Microcystis aeruginosa

Gumbo,; J, R; T, E

doi:10.5897/ajb10.1311

Cited by 20 publications

(18 citation statements)

References 21 publications

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“…This kind of visualization enables us to detect otherwise invisible cells or cyanobacterial cell “ghosts” [13]. These are frequently smaller, as the result of cytoskeleton collapse to the degraded interior described also as honeycomb skeletal structure in the SEM microscopy study by Gumbo and Cloete (2011) [18]. Some difference in cytoskeleton labeling between the two MC producing and the MC the non-producing strain are apparent.…”

Section: Discussionmentioning

confidence: 96%

UVB Radiation as a Potential Selective Factor Favoring Microcystin Producing Bloom Forming Cyanobacteria

2013

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Due to the stratospheric ozone depletion, several organisms will become exposed to increased biologically active UVB (280–320 nm) radiation, not only at polar but also at temperate and tropical latitudes. Bloom forming cyanobacteria are exposed to UVB radiation on a mass scale, particularly during the surface bloom and scum formation that can persist for long periods of time. All buoyant species of cyanobacteria are at least periodically exposed to higher irradiation during their vertical migration to the surface that usually occurs several times a day. The aim of this study is to assess the influence on cyanobacteria of UVB radiation at realistic environmental intensities. The effects of two UVB intensities of 0.5 and 0.99 W/m2 in up to 0.5 cm water depth were studied in vitro on Microcystis aeruginosa strains, two microcystin producing and one non-producing. After UVB exposure their ability to proliferate was estimated by cell counting, while cell fitness and integrity were evaluated using light microscopy, autofluorescence and immunofluorescence. Gene damage was assessed by TUNEL assay and SYBR Green staining of the nucleoide area. We conclude that UVB exposure causes damage to the genetic material, cytoskeletal elements, higher sedimentation rates and consequent cell death. In contrast to microcystin producers (PCC7806 and FACHB905), the microcystin non-producing strain PCC7005 is more susceptible to the deleterious effects of radiation, with weak recovery ability. The ecological relevance of the results is discussed using data from eleven years’ continuous UVB radiation measurements within the area of Ljubljana city (Slovenia, Central Europe). Our results suggest that increased solar radiation in temperate latitudes can have its strongest effect during cyanobacterial bloom formation in spring and early summer. UVB radiation in this period may significantly influence strain composition of cyanobacterial blooms in favor of microcystin producers.

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Section: Discussionmentioning

confidence: 96%

UVB Radiation as a Potential Selective Factor Favoring Microcystin Producing Bloom Forming Cyanobacteria

2013

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“…TD compounds, such as compounds 2,4,6,14,15,16,20, and 21, exhibited IC 50 values <4 µM for all HABs studied, which makes them possible candidates for algicidal application. In contrast, compounds 3 and 5 exhibited relatively high IC 50 values ranging from 35 to 120 µM, which suggests that the HABs are tolerant to these TDs.…”

Section: Resultsmentioning

confidence: 97%

“…Of the compounds examined, compounds 4, 6,7,12,13,14,15,16,17,18,19,20,21,22,22, and 26 were the most potent against C. polykrikoides exhibiting IC 50 values <1 µM. In particular, compounds 7, 13, and 27 were extremely competent and selective against C. polykrikoides and exhibited an IC 50 value ranging from 0.1 to 2 µM, while C. marina and H. akashiwo showed an IC 50 value ranging from 30 to 130 µM.…”

Section: Resultsmentioning

confidence: 99%

“…Yellow loess is effective in sedimenting dinoflagellates [13,14]. However, ruptured or damaged cells may release intracellular toxins into the surrounding water, which require the use of expensive removal processes, such as activated carbon and/or oxidative ozone and chlorine [15]. Mechanical and physicochemical methods have been devised in an attempt to manage HABs with limited success [16][17][18].…”

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confidence: 99%

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Thiazolidinediones as a Novel Class of Algicides Against Red Tide Harmful Algal Species

Kim

Duong

et al. 2010

Appl Biochem Biotechnol

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This paper reports the synthesis of 28 thiazolidinedione derivatives along with their algicidal activity against microalgae causing harmful algal blooming. Among the 28 compounds tested, most showed effective algicidal activity against Heterosigma akashiwo, Chattonella marina, and Cochlodinium polykrikoides, while non-harmful algae were relatively tolerant to these thiazolidinedione derivatives. Compounds 6, 13, and 22 were the most potent against C. polykrikoides with IC₅₀ values <0.5 µM. Among the thiazolidinedione derivatives tested, compounds 7, 13, 27, and 28 were extremely competent and selective to C. polykrikoides with IC₅₀ values ranging from 0.1 to 2 µM, while C. marina and H. akashiwo showed an IC₅₀ value ranging from 30 to 130 µM. These results show that some thiazolidinedione derivatives can act as potent algicides against harmful algal blooms.

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“…The previous studies of light and electron microscopy studies (Gumbo and Cloete, 2011) and this study formed the basis for the development of a model describing the mechanism of Microcystis lysis.…”

Section: Introductionmentioning

confidence: 99%

The mechanism of Microcystis aeruginosa death upon exposure to Bacillus mycoides

Gumbo¹,

Cloete²

2011

Physics and Chemistry of the Earth, Parts A/B/C

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Electron microscopy observations revealed at least two mechanisms of M. aeruginosa cell death upon exposure to B. mycoides i.e. cell membrane lysis and shadowing of algal cells leading to photo-inhibition. There were ultra-structural changes that occurred in bacteria treated M. aeruginosa cells. SEM images showed swollen M. aeruginosa cells due to cell membrane damage and increased osmotic pressure. The production of intracellular stress related structures by M. aeruginosa indicated cell stress as a result of bacteria causing shadowing and photo -inhibition affecting the photosynthetic system. There is evidence, which showed that Bacillus mycoides B16 might be an ectoparasite during the lysis of Microcystis cells and exhibit multicellular forms that are Bdellovibriolike bacteria during the last stages lysis of Microcystis cells in order to survive an adverse external environment that was nutrient limited. The mechanism of cyanobacterial lysis may involve changes in ultrastructure of Microcystis aeruginosa, possibly affecting energy sources and the photosynthetic system after exposure to bacteria. This may lead to the death of the cyanobacteria after exhaustion of energy sources and loss of nutrients to the predator bacteria, B. mycoides B16. A better understanding of the interactions between B. mycoides 16 and M. aeruginosa is important for the development of a biological control agent and ultimately the management of harmful algal blooms dominated by M. aeruginosa.

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Light and electron microscope assessment of the lytic activity of Bacillus on Microcystis aeruginosa

Cited by 20 publications

References 21 publications

UVB Radiation as a Potential Selective Factor Favoring Microcystin Producing Bloom Forming Cyanobacteria

UVB Radiation as a Potential Selective Factor Favoring Microcystin Producing Bloom Forming Cyanobacteria

Thiazolidinediones as a Novel Class of Algicides Against Red Tide Harmful Algal Species

The mechanism of Microcystis aeruginosa death upon exposure to Bacillus mycoides

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