Diversity of cyanobacteria in biological soil crusts and evaluation of cellulolytic and hemicellulolytic profile

Author(s)

Nathali Maria Machado de Lima

• Document type: Master's Dissertation
• Press: São José do Rio Preto. 2018-09-06.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Biociências Letras e Ciências Exatas. São José do Rio Preto
• Defense date: 2016-10-31
• Advisor: Luis Henrique Zanini Branco

Abstract

Biological soil crusts (BSCs) are communities potentially composed of cyanobacteria, green algae, micro fungi, bacteria, lichens and mosses. They occur in a variety of soils and climatic regions around the world, playing important roles as giving soil stability protecting against erosive forces, accumulating and increasing residence time for water in soil, besides promoting germination and performing nitrogen and carbon fixation. Biological soil crusts from hot deserts are frequently composed of cyanobacteria and lichens, and the cyanobacteria are considered the first colonizers in structuring the crust, being followed by other groups of organisms. A lot of new genera and species have been described based on crusts investigations and this fact also emphasizes the necessity of works on those communities. Due to environmental conditions, as soil exposition and phytophysiognomy, the biome Cerrado (Savannah) was chosen to be the place for studies on cyanobacterial assemblages of biological soil crusts. Besides, due to previous studies that indicate the production capability of celulolitic and hemicelulolitic enzymes by heterocytous cyanobacteria and the common presence of this kind of cyanobacteria in biological soil crusts, analyses of such production were also conducted. In this way, the studies aimed to contribute with knowledge about cyanobacterial biodiversity in biocrusts and evaluate the bioprospection capability of cyanobacterial from these biocrusts. Therefore, BSCs were sampled at the National Parks of Serra da Canastra (Minas Gerais State) and Serra do Cipó (Minas Gerais State), at the State Park of Furnas do Bom Jesus (São Paulo State) and in the region of the municipality of Caldas Novas (Goiás State). The cyanobacteria found in the samples had their morphology analyzed from the natural and cultivated conditions. Besides, molecular and enzymatic analysis were carried out. The results summarized 28 morphotypes from 31 populations, which 12 were identified at specie level (three of them need identity confirmation = cf) and 16 were identified only at genus level. Nineteen populations also were studied with molecular methods, through partial sequencing of 16S rRNA gene and complete sequencing of the Internal Transcribed Space Region (16S-23S ITS). In addition, six populations also were explored as possible enzymatic producers. Among the found genera, many are cyanobacteria frequently found in BSCs distributed around the world, however, some identifications at specific level were not possible due to considerable divergences in comparison with described taxa. The molecular analysis reaffirmed and emphasized the polyphyletic nature of Leptolyngbya, Nostoc and Calothrix, reinforced the existence of a new genus close related with Wilmottia and Microcoleus and presented a new group composed, until now, of one species represented by two populations. This group showed molecular sequences related with Brasilonema, however, the specimens are true branched, what requires more detailed studies to confirm the identification of the populations. In this way, the morphological and molecular analyses showed the wide diversity whose has not been accessed in poorly investigated places and habitats and reinforced the contribution of this work in focusing the cyanobacterial flora of crusts of Brazilian savannah area for the first time. The enzymatic activity analysis revealed that the strains studied did not produce celulolitic or hemicelulolitic compounds, having as possible explanations the absence of the production ability or the inefficiency of the utilized method. Either way, the results emphasized the necessity of studies in this area, mainly because of the difficulty in find producer strains and the lack of knowledge about which could be the factors influencing the strains in activate or select differently their metabolism. In general, our results presented for the first time the cyanobacterial composition for BSCs from Brazil and indicated a diverse, and sometimes, unknown flora. These results provided foundation and opened doors to investigations inside the biodiversity knowledge with biological soil crusts. Complementary, these works compound the basis for investigations in the ecology of extreme environments (as Caatinga and Cerrado), permiting studies about successional ecology, primary productivity, flow of nutrients and soil dynamics. (AU)

• FAPESP's process: 14/06245-8 - Diversity of cyanobacteria in biological crusts and evaluation of cellulolytic and hemicellulolytic activity.
• Grantee: Náthali Maria Machado de Lima
• Support Opportunities: Scholarships in Brazil - Master