Characteristics and roles of <i>Microcystis</i> extracellular polymeric substances (EPS) in cyanobacterial blooms: a short review

Liu, Lizhen; Huang, Qi; Qin, Boqiang

doi:10.1080/02705060.2017.1391722

Cited by 65 publications

(41 citation statements)

References 66 publications

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“…Finally, it is necessary to mention that in natural environments the cells of M. aeruginosa are normally found forming colonies, which are more protected from the external environment than single cells because they are embedded in extracellular polymeric substances (EPS, Liu et al 2018). Therefore, taking into account that the experiments in this study were performed with single-celled culture inoculums, we would surely be underestimating the capacity of adaptation of the population in nature.…”

Section: Discussionmentioning

confidence: 97%

Adaptation of the toxic freshwater cyanobacterium Microcystis aeruginosa to salinity is achieved by the selection of spontaneous mutants

Melero‐Jiménez

Martín‐Clemente

García‐Sánchez

et al. 2019

Phycological Research

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SUMMARY The cyanobacterium Microcystis aeruginosa causes most of the harmful toxic blooms in freshwater ecosystems. Some strains of M. aeruginosa tolerate low‐medium levels of salinity, and because salinization of freshwater aquatic systems is increasing worldwide it is relevant to know what adaptive mechanisms allow tolerance to salinity. The mechanisms involved in the adaptation of M. aeruginosa to salinity (acclimation vs. genetic adaptation) were tested by a fluctuation analysis design, and then the maximum capacity of adaptation to salinity was studied by a ratchet protocol experiment. Whereas a dose of 10 g NaCl L−1 completely inhibited the growth of M. aeruginosa, salinity‐resistant genetic variants, capable of tolerating up to 14 g NaCl L−1, were isolated in the fluctuation analysis experiment. The salinity‐resistant cells arose by spontaneous mutations at a rate of 7.3 × 10−7 mutants per cell division. We observed with the ratchet protocol that three independent culture populations of M. aeruginosa were able to adapt to up to 15.1 g L−1 of NaCl, suggesting that successive mutation‐selection processes can enhance the highest salinity level to which M. aeruginosa cells can initially adapt. We propose that increasing salinity in water reservoirs could lead to the selection of salinity‐resistant mutants of M. aeruginosa.

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Section: Discussionmentioning

confidence: 97%

Adaptation of the toxic freshwater cyanobacterium Microcystis aeruginosa to salinity is achieved by the selection of spontaneous mutants

Melero‐Jiménez

Martín‐Clemente

García‐Sánchez

et al. 2019

Phycological Research

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“…When these layers are present in cyanobacteria, they are likely to perform a protective role against ultraviolet radiation, oxidation, toxic compounds, desiccation and predation by protozoans [14]. More specifically, studies have shown that these external layers are essential for maintaining the colonial morphology of cyanobacteria, and they participate in a wide array of physiological processes, including cell-to-cell interactions, adhesion and aggregation, which further influence the fate of blooms [15]. Cyanobacterial external layers exhibit some typical characteristics that provide a competitive advantage over other competitors throughout its life cycle.…”

Section: Introductionmentioning

confidence: 99%

The Role of Cyanobacterial External Layers in Mass Transfer: Evidence from Temperature Shock Experiments by Noninvasive Microtest Technology

Yan¹,

Liu²,

Li³

et al. 2020

Microorganisms

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Groundwork on cyanobacterial external layers is crucial for an improved understanding of the persistent dominance of cyanobacteria in freshwaters. In this study, the role of two morphotypes of external layers in Microcystis and Nostoc in mass transfer and instantaneous temperature shock were explored by noninvasive microtest technology (NMT) after a series of pretreatments, to obtain the external layers retained or stripped samples. The results showed no statistical influence on photosynthetic activity between retained and stripped samples in both Microcystis and Nostoc. External-layer-retaining strains had higher net O2 effluxes than stripped strains. Moreover, the net NH4+ influx was significantly higher for the sheath retaining Nostoc than for the stripped sample, indicating that external layers might be an important feature driving mass transfer in cyanobacteria. However, the role of slime in NH4+ absorption was limited compared with that of sheath. In addition, external-layer-retaining strains exhibited a longer response time to instantaneous temperature shock, greater net O2 effluxes at a 4 °C shock and lower net O2 influx at a 35 °C shock, which were interpreted as reflecting a tolerance to temperature fluctuation over short time scales via a buffer function of external layers to stabilize cell activity, ameliorating the efficiency of photosynthesis and respiration. These results advance current knowledge regarding the external layers, especially the dense sheath, involved in the mass transfer in cyanobacteria, and provide new clues concerning the adaptive strategies of cyanobacteria under global climate changes.

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“…EPS are crucial for the development of biofilms, providing fundamental cohesive force for the colonization of solid surfaces (Liu et al, 2018). Our findings suggest that exopolysaccharides of the EPS layer substantially inhibit EET processes by increasing charge transfer resistance.…”

Section: Resultsmentioning

confidence: 99%

Mediation of Extracellular Polymeric Substances in Microbial Reduction of Hematite by Shewanella oneidensis MR-1

Gao

Liu

et al. 2019

Front. Microbiol.

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Extracellular electron transfer (EET) plays a fundamental role in microbial reduction/oxidation of minerals. Extracellular polymeric substances (EPS) surrounding the cells constitute a matrix that separates the cell’s outer membrane from insoluble minerals and environmental fluid. This study investigated the effects of EPS on EET processes during microbial reduction of hematite by the iron-reducing strain Shewanella oneidensis MR-1 (MR-1). Electrochemical characterization techniques were employed to determine the influence of EPS components on the redox ability of MR-1. Cells with removed EPS exhibited approximately 30% higher hematite reduction than regular MR-1 cells, and produced a current density of 56 μA cm -2 , corresponding to 3–4 fold that of regular MR-1. The superior EET of EPS-deprived cells could be attributed to direct contact between outer membrane proteins and hematite surface, as indicated by more redox peaks being detected by cyclic voltammetry and differential pulse voltammetry. The significantly reduced current density of MR-1 cells treated with proteinase K and deoxyribonuclease suggests that the electron transfer capacity across the EPS layer depends mainly on the spatial distribution of specific proteins and electron shuttles. Exopolysaccharides in EPS tend to inhibit electron transfer, however they also favor the attachment of cells onto hematite surfaces. Consistently, the charge transfer resistance of cells lacking EPS was only 116.3 Ω, approximately 44 times lower than that of regular cells (5,139.1 Ω). These findings point to a negative influence of EPS on EET processes for microbial reduction/oxidation of minerals.

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Characteristics and roles of Microcystis extracellular polymeric substances (EPS) in cyanobacterial blooms: a short review

Cited by 65 publications

References 66 publications

Adaptation of the toxic freshwater cyanobacterium Microcystis aeruginosa to salinity is achieved by the selection of spontaneous mutants

Adaptation of the toxic freshwater cyanobacterium Microcystis aeruginosa to salinity is achieved by the selection of spontaneous mutants

The Role of Cyanobacterial External Layers in Mass Transfer: Evidence from Temperature Shock Experiments by Noninvasive Microtest Technology

Mediation of Extracellular Polymeric Substances in Microbial Reduction of Hematite by Shewanella oneidensis MR-1

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