Explore the vast range of titles available.

Biological soil crusts (BSCs) are common in arid and semi-arid ecosystems and enhance soil stability and fertility. Highway slopes severely deplete the soil ecological structure and soil nutrients, hindering plant survival. The construction of highway slope BSCs under human intervention is critical to ensure the long-term stable operation of the slope ecosystem. This study investigated the variation rules and interaction mechanisms between soil nutrients and microbial communities in the subsoil BSCs on highway slopes. Bacterial 16S rRNA high-throughput sequencing was employed to investigate the dynamic compositional changes in the microbial community and perform critical metabolic predictive analyses of functional bacteria. This study revealed that the total soil nitrogen increased significantly from 0.557 to 0.864 g/kg after artificial inoculation with desert Phormidium tenue and Scytonema javanicum . Actinobacteria (44–48%) and Proteobacteria (28–31%) were the dominant phyla in all samples. The abundance of Cyanobacteria, Cytophagaceae, and Chitinophagaceae increased significantly after inoculation. PICRUST analysis showed that the main metabolic pathways of soil microorganisms on highway slopes included cofactor and vitamin, nucleotide, and amino acid metabolisms. These findings suggest that the artificial inoculation with Phormidium tenue and Scytonema javanicum could alter soil microbial distribution to promote soil development on highway slopes toward nutrient accumulation.

Aims Biological soil crusts (BSCs) could improve severe environment ecological conditions by increasing soil moisture, soil nitrogen concentration, and so on. In order to control desertification and recover the destroyed soil fertility utilizing a new means using BSCs, the soil surface was artificially inoculated with Microcoleus vaginatus and Scytonema javanicum. Relationships between the development of the artificially induced biological soil crusts and the distribution and dynamic changes of nitrogen and phosphorus in the soil crusts have been analyzed. Methods Crusts of different ages were investigated by measuring soil physical and chemical factors, such as moisture, pH, total and available N content, and total and available P, which were correlated with the depths of the crusts. Results This study found that the types of color, shape, and species components of the algal crusts increased with crust development. Soil moisture, total N, available N, and available P increased gradually with crust growth. Soil with crusts was wetter than the controlled naked sandy soil, and a significant correlation was observed between biomass and total nitrogen (r= 0.946, P= 0.015). Soil pH was lower than that of control. The scytonemin on the soil surface was exceptionally higher than the other pigments, and all the pigments were mainly distributed at the soil surface level. Though the crusts were mainly distributed on soil surface, the available P was mainly stored below the crust layer. Conclusions Pearson correlation tests indicated that artificially inoculated biological crusts could improve soil fertility and micro-environment of the top soil: The development of artificially induced BSCs was very well, and this was favorable to inducing the following crust succession.

Cultivation of desert cyanobacteria in wastewater can lead to the optimal redistribution of regional resources and is likely to solve two global problems, i.e., wastewater pollution and desertification. However, the potential of using wastewater instead of traditional artificial culture media to cultivate sand-consolidating cyanobacteria for desert management is not well understood. This study compares undistilled and distilled wastewater with an artificial culture medium (BG11 0 ) to explore the potential of wastewater as a replacement culture medium for Scytonema javanicum . The results show that the photosynthetic activity ( F v / F m ) of S. javanicum was inhibited in the undistilled wastewater and was lower than that in distilled water and the culture medium. The lowest Chl- a concentration and the highest concentration in BG11 0 were found in distilled wastewater. However, there was no difference in the biomass (dry weight) between the undistilled wastewater and BG11 0 at the end of the experiment. After long-term dry storage of the biomass collected after cultivation, there was no difference in the photosynthetic recovery between S. javanicum cultivated in undistilled wastewater and that cultivated in BG11 0 . Accordingly, although wastewater depressed the Chl- a content, it did not affect the biomass accumulation and subsequent photosynthetic recovery after long-term storage. The results reveal the significant potential of cultivating sand-consolidating cyanobacterium in wastewater and using this technology as a new nutrient redistribution method in human settlements and desert areas.

Artificial biological soil crusts (ABSCs), formed by inoculating Microcoleus vaginatus Gom. and Scytonema javanicum Born. et Flah. onto the topsoil of desert dunes, proved to be effective tools for the stabilization of moving dunes and promotion of soil fertility. As dominant driving forces in arid habitats, the abiotic environmental conditions of undulating dunes produce a gradient of abiotic stresses on cyanobacteria. Cyanobacteria are considered pioneering phototrophs in early soil crust communities in deserts. In this study, the development of ABSCs under various environmental site conditions was investigated using 16S rRNA-based polymerase chain reaction, denaturing gradient gel electrophoresis (DGGE), and soil property measurements. After inoculation in 2002 and long-term development, patchy moss crusts were observed on the dunes. All of the available sequenced bands in the DGGE gels belonged to Oscillatoriales and Nostocales. The dominant Nostocales genus in the ABSCs was still Scytonema; however, more Oscillatoriales genera were identified, which belonged to Microcoleus and Phormidium. The cyanobacterial compositions of different slope types were significantly distinct (p < 0.05), particularly those from windward slopes. The crusts of the top-dune slopes were more heterogeneous. In addition, the soil physicochemical properties and richness indices of the windward slopes were significantly lower than those of the leeward and interdune slopes (p < 0.05). Compared with uninoculated control dunes, all of the inoculated dunes had far higher biodiversities.

The adaption capability of microalgae species to intense UV-B radiation is an important feature for their survival under the harsh growth conditions they have to face when used for inoculating unconsolidated sand soils in desert areas. In this study, the responses of photosynthetic activity, reactive oxygen species (ROS) generation, and DNA strand breaks to UV-B radiation in four microalgae isolated from artificially induced biological soil crusts were investigated. It was found that low UV-B doses easily inhibited the photosynthetic activity and induced serious DNA damage in Chlorella vulgaris. Microcoleus vaginatus showed the capability to withstand only moderate doses of UV-B, while Nostoc was capable of facing high doses of UV-B due to its lower generation of ROS and higher capability to repair photosystem II (PSII) and DNA damages. On the other hand, Scytonema javanicum showed additional strategies to survive UV-B irradiance, namely the closure of PSII when ROS generation increased rapidly, in addition to a high repair ability of PSII and DNA damage. The results obtained point out different resistance and defense mechanisms of the four microalgae in response to UV-B irradiance and suggest that the strain of Nostoc sp. tested is the most suitable for surviving under the high UV irradiation levels typical of desertified areas.

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.

Repression of alkaline phosphatase (APase) activity in four taxonomically different cyanobacteria Anabaena flosaquae, Calothrix brevissima, Scytonema javanicum and Hapalosiphon intricatus by rifampicin and chloramphenicol led to the conclusion that enzyme synthesis is under transcriptional control. A mutant isolated in Nostoc muscorum after mutagenesis with NTG was found to be defective in APase activity (APase super(def)). The mutant showed nearly 90% growth compared to wild type strain in the presence of inorganic phosphate (P sub(i)). The wild type Nostoc muscorum showed some growth (33% compared to P sub(i)) in the presence of organic phosphate but the growth of the APase super(def) mutant was negligible under these conditions since it lacks APase activity. APase activity and phosphate uptake functions were phosphate repressible in the wild type strain. Phosphate uptake in the mutant was comparable to the wild type cyanobacterium. The mutant was also able to accumulate polyphosphate granules like the wild type.

Alkaline phosphatase (phosphomonoesterase i.e. PMEase) activity in heterocystous cyanobacteria Anabaena flos-aquae, Nostoc calcicola, Calothrix brevissima, Scytonema javanicum and Hapalosiphon intricatus is known to be temperature and pH dependent. Maximum level of enzyme activity was recorded at either 35 degrees C or 37.5 degrees C. Also, the cell bound phosphomonoesterase enzyme was shown to exhibit pH optima of 10.0 or 10.2. A thermo-tolerant (tr) mutant isolated after MNNG (N-methyl-N'-nitro-N-nitrosoguanidine) mutagenesis in Calothrix brevissima exhibited 10 degrees C higher temperature optima and comparatively high pH optima (pH 10.4) for phosphomonoesterase enzyme. The mutant grew with a maximum growth rate (k) at 50 degrees C. Activation energy (Ea) for cyanobacterial strains was in a narrow range between 45 to 52 kJ mol(-1). A little variation in temperature and pH optima was also observed in phosphomonoesterase activity of Calothrix brevissima and its thermo-tolerant mutant while utilizing various organic phosphates as substrate what indicated the substrate dependence temperature and pH optima. Cyanobacterial strains grown at their respective temperature and pH optima differentiated spores less frequently though, coupled with early initiation of spore.