The role of cyanobacterial exopolysaccharides in structuring desert microbial crusts

Mazor, G.

doi:10.1016/0168-6496(96)00050-5

Cited by 90 publications

(137 citation statements)

References 6 publications

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“…Oscillatoria excretes exopolysaccharides (EPS) as it glides, and it forms filaments which can reach several millimeters of length. Those EPS, which are essential for the crust cohesion by trapping mineral particles [21], can act as guides to help the vertically directed gliding of the cyanobacteria [14,22]. This would explain the fast responses encountered.…”

Section: Control Of the Migrationmentioning

confidence: 99%

Hydrotaxis of Cyanobacteria in Desert Crusts

Pringault¹,

García-Pichel

2003

Microb Ecol

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We studied the migration of cyanobacteria in desert crusts from Las Bárdenas Reales (Spain). The crusts were almost exclusively colonized by the filamentous cyanobacterium Oscillatoria, which formed a dense layer approximately 600 lm thick located between 1.5 and 2.1 mm deep. Laboratory and field experiments showed that saturation of the crust with liquid water induced a migration of the cyanobacteria leading to a significant greening of the surface within a few minutes. Under light and rapid evaporation, the green color rapidly disappeared and the crust surface was completely devoid of filaments within 60 min. In contrast, 260 min was required to recover the original white color of the crust when slow evaporation was experimentally imposed. The up and down migration following wetting and drying occurred also in the dark. This demonstrates that light was not a required stimulus. Addition of ATP synthesis inhibitors prevented the cyanobacterium from migrating down into the crust, with filaments remaining on the surface. Therefore, the disappearance of the green color observed during desiccation can only be attributed to an active cyanobacterial motility response to the decrease in the water content. The simplest explanation that can account for the evidence gathered is the presence of a mechanism that links, directly or indirectly, these motility responses to gradients in water content, namely a form of hydrotaxis.

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Section: Control Of the Migrationmentioning

confidence: 99%

Hydrotaxis of Cyanobacteria in Desert Crusts

Pringault¹,

García-Pichel

2003

Microb Ecol

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“…Unlike transient rain crusts, algal crusts are critical to the ecosystems in which they occur. Evidence has shown that they may play important roles in the stabilization of soil surfaces and the improvement of soil structure, contributing significantly to soil fertility of these regions through such processes as nitrogen fixation, excretion of extracellular substances, and retention of soil particles, organic matter and moisture (Johansen, 1993;Liu and Li, 1993;Mazor, 1996;Painter, 1993). Nitrogen fixation by cyanobacteria and lichens (due to their symbiotic cyanobacteria) comprising the crusts is the primary source of nitrogen input in many of the arid ecosystems on a worldwide basis (Evans and Belnap, 1999).…”

Section: Introductionmentioning

confidence: 99%

The vertical microdistribution of cyanobacteria and green algae within desert crusts and the development of the algal crusts

et al. 2003

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Substantial amounts of algal crusts were collected from five different desert experimental sites aged 42, 34, 17, 8 and 4 years, respectively, at Shapotou (China) and analyzed at a 0.1 mm microscale of depth. It was found that the vertical distribution of cyanobacteria and microalgae in the crusts was distinctly laminated into an inorganic-layer (ca.0.00-0.02 mm, with few algae), an algae-dense-layer (ca.0.02-1.0 mm) and an algae-sparselayer (ca.1.0-5.0 mm). It was interesting to note that in all crusts Scytonema javanicum Born et Flah (or Nostoc sp., cyanobacterium), Desmococcus olivaceus (Pers ex Ach., green alga) Laundon and Microcoleus vaginatus Gom. (cyanobacterium) dominated at the depth of 0.02-0.05, 0.05-0.1 and 0.1-1.0 mm, respectively, from the surface. Phormidium tenue Gom. (or Lyngbya cryptovaginatus Schk., cyanobacterium) and Navicula cryptocephala Kutz.(or Hantzschia amphioxys (Ehr.) Grun. and N. cryptocephala together, diatom) dominated at the depth of 1.0-3.0 and 3.5-4.0 mm, respectively, of the crusts from the 42 and 34 year old sites. It was apparent that in more developed crusts there were more green algae and the niches of Nostoc sp., Chlorella vulgaris Beij., M. vaginatus, N. cryptocephala and fungi were nearer to the surface. If lichens and mosses accounted for less than 41.5% of the crust surface, algal biovolume was bigger when the crust was older, but the opposite was true when the cryptogams other than algae covered more than 70%. In addition to detailed species composition and biovolume, analyses of soil physicochemical properties, micromorphologies and mineral components were also performed. It was found that the concentration of organic matter and nutrients, electric conductivity, silt, clay, secondary minerals were higher and there were more micro-beddings in the older crusts than the less developed ones. Possible mechanisms for the algal vertical microdistribtion at different stages and the impact of soil topography on crust development are discussed. It is concluded that biomethods (such as fine species distribution and biovolume) were more precise than mineralogical approaches in judging algal crust development and thus could be a better means to measure the potentiality of algal crusts in desert amelioration.Abbreviations: I.V. -Important Value; PLM -Polarizing Light Microscope; SEM -Scanning Electron Microscopy

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“…Their formation is aided by filamentous sheath−forming species (e.g. Schizothrix, Microcoleus) be− cause the presence of a sheath and mucilage can help protect cells against physical desiccation (Mazor et al 1996;Gupta and Agrawal 2008).…”

Section: Resultsmentioning

confidence: 99%

Relationship of cyanobacterial and algal assemblages with vegetation in the high Arctic tundra (West Spitsbergen, Svalbard Archipelago)

Richter¹,

Pietryka²,

Matuła³

2015

Polish Polar Research

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Abstract:The paper presents the results of a study of cyanobacteria and green algae assem− blages occurring in various tundra types determined on the basis of mosses and vascular plants and habitat conditions. The research was carried out during summer in the years 2009-2013 on the north sea−coast of Hornsund fjord (West Spitsbergen, Svalbard Archipel− ago). 58 sites were studied in various tundra types differing in composition of vascular plants, mosses and in trophy and humidity. 141 cyanobacteria and green algae were noted in the research area in total. Cyanobacteria and green algae flora is a significant element of many tundra types and sometimes even dominate there. Despite its importance, it has not been hitherto taken into account in the description and classification of tundra. The aim of the present study was to demonstrate the legitimacy of using phycoflora in supplementing the descriptions of hitherto described tundra and distinguishing new tundra types. Numeric hierarchical−accumulative classification (MVSP 3.1 software) methods were used to ana− lyze the cyanobacterial and algal assemblages and their co−relations with particular tundra types. The analysis determined dominant and distinctive species in the communities in con− cordance with ecologically diverse types of tundra. The results show the importance of these organisms in the composition of the vegetation of tundra types and their role in the ecosystems of this part of the Arctic.

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The role of cyanobacterial exopolysaccharides in structuring desert microbial crusts

Cited by 90 publications

References 6 publications

Hydrotaxis of Cyanobacteria in Desert Crusts

Hydrotaxis of Cyanobacteria in Desert Crusts

The vertical microdistribution of cyanobacteria and green algae within desert crusts and the development of the algal crusts

Relationship of cyanobacterial and algal assemblages with vegetation in the high Arctic tundra (West Spitsbergen, Svalbard Archipelago)

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