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Microbial secreted exopolysaccharides of induced biological soil crusts in Inner Mongolian desert soils: chemical characteristics and role in affecting water-soil relations
No full textRole of polysaccharides produced by cyanobacteria in affecting the structure and the hydrological properties of the soi
Biological soil crusts: from ecology to biotechnology
No full textWhile the beneficial effects of algalization to improve agricultural fields are well known, a limited number of inoculation studies
have been so far carried out in prohibitive constrained ecosystems, where soil is unconsolidated, with very limited nutrient levels and high
abiotic stress levels. Recent results show that some cyanobacterial strains such as the non-heterocystous exopolysaccharide-producer
Microcoleus vaginatus, are able to grow in such conditions developing quickly into biological soil crusts, kicking off beneficial microbiological
processes potentially able to shift the state of the environment. This paper reviews the state of the art of this technology, pointing
out the existing gaps to fulfill in order to address different issues, including land rehabilitation and desertification counteractio
Role of Cyanobacterial Exopolysaccharides in Phototrophic Biofilms and in Complex Microbial Mats
Get PDFExopolysaccharides (EPSs) are an important class of biopolymers with great ecological importance. In natural environments, they are a common feature of microbial biofilms, where they play key protective and structural roles. As the primary colonizers of constrained environments, such as desert soils and lithic and exposed substrates, cyanobacteria are the first contributors to the synthesis of the EPSs constituting the extracellular polymeric matrix that favors the formation of microbial associations with varying levels of complexity called biofilms. Cyanobacterial colonization represents the first step for the formation of biofilms with different levels of complexity. In all of the possible systems in which cyanobacteria are involved, the synthesis of EPSs contributes a structurally-stable and hydrated microenvironment, as well as chemical/physical protection against biotic and abiotic stress factors. Notwithstanding the important roles of cyanobacterial EPSs, many aspects related to their roles and the relative elicited biotic and abiotic factors have still to be clarified. The aim of this survey is to outline the state-of-the-art of the importance of the cyanobacterial EPS excretion, both for the producing cells and for the microbial associations in which cyanobacteria are a key component
The induction of biological soil crusts: an environmental biotechnology based on the exploitation of phototrophic microorganisms
No full textThe lecture was focused on the recent results obtained by applying the biotechnology based on large scale cyanobacterial inoculation and BSC induction, and stresses how the potential of cyanobacterial inoculation can be translated in a flexible technology applicable in different contexts such as the stabilization and fertilization of aeolian sandy lands in arid and semiarid environment
Role of biological soil crusts in CO2 fixation and soil rehabilitation in desert environments
No full textInoculation of sandy dunes with cyanobacteria for the stabilization of the sand by the formation of induced biological soil crust
Microbial secreted exopolysaccharides of induced biological soil crusts in Inner Mongolian desert soils: chemical characteristics and role in affecting water-soil relations
No full textIn nature, Biological Soil Crusts (BSCs) are highly specialized communities constituted by cyanobacteria, green
algae, fungi, mosses, lichens and heterotrophic bacteria. They inhabit the first few millimeters of the soil surface in
arid and semiarid environments where, due to harsh environmental conditions, the growth of most of the other
organisms is restricted. The development of BSCs is widely recognized as beneficial to soil fertility due to their
contribution to the stabilization of soils and to the increase in their carbon and moisture content. The induction of
BSCs through spray-inoculation of sandy soils with suitable cyanobacteria was shown to be a beneficial and
exploitable tool to trigger soil rehabilitation and counteract desertification in a number of experimental sites in Inner
Mongolian deserts. An important role in these processes is played by the extracellular polysaccharidic (EPS) matrix
embedding microbial cells and soil particles in BSCs. The present study was aimed at investigating the molecular and
chemical features of the EPSs and the degradation processes of the polysaccharidic matrix in induced BSCs (IBSCs)
of different ages displayed within an investigation area in Hobq Desert (Inner Mongolia, China). The influence of the
EPSs in affecting the hydrological behaviour of IBSCs as well as in capturing and maintaining moisture was also
investigated.
Two operationally-defined EPS fractions, the colloidal (C-EPS) and the EDTA extractable (tightly bound, TB-EPS)
fractions, were analyzed. In BSCs, C-EPSs are loosely bound to cells and sediments while TB-EPSs are tightly bound
to the crustal biotic and abiotic constituents of the crusts. C-EPS showed to be mostly constituted by sugar fractions
with MW distributed in the range 2000 - 76 kDa and in the range 64 - 0.34 kDa. Conversely, the TB-EPSs showed to
be prominently constituted by one fraction having a MW in the range 2000 - 76 kDa. The presence of EPSs in IBSCs
also induced a significant decrease in the hydraulic conductivity of IBSCs in comparison with bare sandy soil and
contributed to their capability of trapping and retaining humidity.
The results obtained suggest that C-EPSs, which are dispersed in the soil, are more easily degradable by the
heterotrophic microflora, while the TB-EPSs, which are characterized by a high MW, play a key role in giving a
structural stability to the crusts and in affecting their hydrological behavior
Complex role of the exopolysaccharidic matrix in biological soil crusts
No full textIn arid and semiarid environments, soil carbon sequestration (CO2 fixation) by
cyanobacteria and by biological soil crusts (BSC) is considered an eco-friendly and natural
process to increase soil C content and a viable pathway to contrast desertification and to favor
soil rehabilitation. Within this context, inoculation-based techniques with exopolysaccharideproducing cyanobacteria have proved to be a viable and sustainable pathway to increase soil
biomass, soil stabilization, and to increase soil fertility. In this presentation, a particular focus
will be given on the role of the extracellular polysaccharidic matrix (EPM) synthesized by
cyanobacteria in giving the structure to natural or induced BSCs and to enhance their water
trapping and retaining capability. EPM was extracted with methods aimed at separately
removing the tightly bound exopolysaccharidic fraction (TB-EPS) and the loosely bound
exopolysaccharidic fraction (colloidal EPS; C-EPS) from BSCs having different ages. The
fractions were analyzed in terms of monosaccharidic composition, and molecular weight (MW)
distribution. We observed that the relative amounts of uronic acids increase in the EPM with the
age of the crusts, implying advantages for the community-water relations. In addition, we also
Abstracts – Third International Workshop on Biological Soil Crusts
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observed significant differences in MW distribution between the two EPS fractions, being TBEPS mostly composed by one molecular fraction having high MW, while C-EPS showed to be
also composed by low MW fractions. This difference suggests distinct roles of TB-EPS and CEPS fractions within the crust system. Indeed, TB-EPS most likely affects BSC structure and
water-retaining properties, while C-EPS most likely contributes to the intake of C in the soil,
thus favoring the growth of the chemoheterotrophic microbial community. The role of EPM in
water capture from non-rainfall sources, water maintenance at the topsoil, and in maintaining a
high water potential was also shown
The use of exopolysaccharide-producing cyanobacteria as biosorbents to remove copper from industrial wastewaters
No full textThe accumulation of heavy metals in water bodies represent a widespread cause of pollution, and poses the need
to develop novel technologies to remove metals at the source, abating the costs of the commonly used chemical
and physio-chemical methods. The use of cyanobacteria as biosorbents has been acknowledged as a promising
alternative, due to their charged polysaccharidic envelopes which have affinity for metal ions. Nonetheless, the
reseach must move towards: i) assessing the effectiveness of the process towards complex wastewater solutions
which contain chemical species that can interfere with the sorption process, also considering the characteristics
of the used strains, and ii) developing novel devices that support biomass growth and use, in order to achieve
a scaling up of the process. We compared the specific removal of three cyanobacteria, Cyanothece 16 Som 2,
Cyanothece ET5 and Cyanospira capsulata, towards Cu2+ contained, with various other metals, in two industrial
effluents (one at pH 1.26 and one at pH 10.26). The strains were selected due to their previously assayed affinity
toward Cu2+ in pure solutions (De Philippis et al. 2011). Acid or basic pretreatments (respectively for the acid
and the basic effluent) were performed in the tentative to increase the specific removal. Metal concentration in
solution, before and after the contact with the biomasses, was determined by atomic absorption spectrometry.
Specific removals resulted different to those obtained towards pure metal solutions, likely due to the presence of
other competing ions. Cyanothece 16 Som 2 showed the highest Cu2+ specific removal towards both the effluents.
The pretreatment was effective only in the case of the basic effluent. Results proved the capacity of Cyanothece 16
Som 2 to act as a selective Cu2+ sorbent even in the presence of complex solutions. A novel prototype device is
being projected in order to support the growth and the immobilization of the cyanobacterial biomass for its use in
industrial field.
De Philippis et al. 2011. Applied Microbiology and Biotechnology 92, 697-708
Microbial fixation of CO2 in water bodies and in drylands to combat climate change, soil loss and desertification
No full textThe growing concern for the increase of the global warming effects due to anthropogenic activities raises the challenge of finding novel technological approaches to stabilize CO2 emissions in the atmosphere and counteract impinging interconnected issues such as desertification and loss of biodiversity.Biological-CO2 mitigation, triggered through biological fixation, is considered a promising and eco-sustainable method, mostly owing to its downstream benefits that can be exploited. Microorganisms such as cyanobacteria, green algae and some autotrophic bacteria could potentially fix CO2 more efficiently than higher plants, due to their faster growth. However, multiple factors have to be optimized for maximum rate of CO2 fixation by these microorganisms. The design of photobioreactors, the optimization of culture conditions including the optimal concentration of CO2 in the provided gas, the use of metabolic engineering and the use of dual purpose systems for the treatment of wastewater and production of biofuels and high value products within a biorefinery, among others, have to be developed and tested for cost-effective CO2 sequestration. In arid and semiarid environments, soil carbon sequestration (CO2 fixation) by cyanobacteria and Biological Soil Crusts represent an eco-friendly and natural process to increase soil C content, and a viable pathway to soil restoration after one disturbance event. Within this context, inoculation-based techniques have proved to be a viable and sustainable pathway to increase soil biomass, soil stabilization and to increase soil fertility.The growing concern for the increase of the global warming effects due to anthropogenic activities raises the challenge of finding novel technological approaches to stabilize CO2 emissions in the atmosphere and counteract impinging interconnected issues such as desertification and loss of biodiversity. Biological-CO2 mitigation, triggered through biological fixation, is considered a promising and eco-sustainable method, mostly owing to its downstream benefits that can be exploited. Microorganisms such as cyanobacteria, green algae and some autotrophic bacteria could potentially fix CO2 more efficiently than higher plants, due to their faster growth. Some examples of the potential of biological-CO2 mitigation are reported and discussed in this paper.In arid and semiarid environments, soil carbon sequestration (CO2 fixation) by cyanobacteria and biological soil crusts is considered an eco-friendly and natural process to increase soil C content and a viable pathway to soil restoration after one disturbance event. Another way for biological-CO2 mitigation intensively studied in the last few years is related to the possibility to perform carbon dioxide sequestration using microalgae, obtaining at the same time bioproducts of industrial interest. Another possibility under study is the exploitation of specific chemotrophic bacteria, such as Ralstonia eutropha (or picketii) and related organisms, for CO2 fixation coupled with the production chemicals such as polyhydroxyalkanoates (PHAs).In spite of the potential of these processes, multiple factors still have to be optimized for maximum rate of CO2 fixation by these microorganisms. The optimization of culture conditions, including the optimal concentration of CO2 in the provided gas, the use of metabolic engineering and of dual purpose systems for the treatment of wastewater and production of biofuels and high value products within a biorefinery concept, the design of photobioreactors in the case of phototrophs are some of the issues that, among others, have to be addressed and tested for cost-effective CO2 sequestration
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