The phylum Acidobacteria is one of the most widespread and abundant on the planet, yet remarkably our knowledge of the role of these diverse organisms in the functioning of terrestrial ecosystems remains surprisingly rudimentary. This blatant knowledge gap stems to a large degree from the difficulties associated with the cultivation of these bacteria by classical means. Given the phylogenetic breadth of the Acidobacteria, which is similar to the metabolically diverse Proteobacteria, it is clear that detailed and functional descriptions of acidobacterial assemblages are necessary. Fortunately, recent advances are providing a glimpse into the ecology of members of the phylum Acidobacteria. These include novel cultivation and enrichment strategies, genomic characterization and analyses of metagenomic DNA from environmental samples. Here, we couple the data from these complementary approaches for a better understanding of their role in the environment, thereby providing some initial insights into the ecology of this important phylum. All cultured acidobacterial type species are heterotrophic, and members of subdivisions 1, 3, and 4 appear to be more versatile in carbohydrate utilization. Genomic and metagenomic data predict a number of ecologically relevant capabilities for some acidobacteria, including the ability to: use of nitrite as N source, respond to soil macro-, micro nutrients and soil acidity, express multiple active transporters, degrade gellan gum and produce exopolysaccharide (EPS). Although these predicted properties allude to a competitive life style in soil, only very few of these predictions have been confirmed via physiological studies. The increased availability of genomic and physiological information, coupled to distribution data in field surveys and experiments, should direct future progress in unraveling the ecology of this important but still enigmatic phylum.

Soils from the Brazilian Cerrado are nutrient-poor, acidic, and aluminum-rich. A previous study revealed that members of the phylum Acidobacteria were predominant in these oligotrophic soils. Five acidobacteria from Cerrado soil were isolated on VL-55 medium containing 0.05% of xylan as carbon source. All isolates belong to the Acidobacteria subdivision 1, and their 16S rRNA showed similarities of 94.2%–96% with Acidobacterium capsulatum or 98.6% with Edaphobacter aggregans. All isolates were able to sustain growth in a wide range of carbon source concentrations. Growth occurred in all concentrations of arabinose, dextrose, and xylose; only one isolate did not grow on fructose. Isolates grew poorly on N-acetyl-d-glucosamine at all concentrations tested. In general, increasing concentrations of these monosaccharides did not inhibit growth rates. Isolates exhibited growth on solid medium containing xylan, carboxymethyl cellulose, and colloidal chitin; however, growth was observed on solid medium that did not contain these polysaccharides. These isolates may be able to use the solidifying agents tested (gellan gum or agar) as carbon source. This interpretation is supported by the absence of growth in liquid media containing chitin or carboxymethyl cellulose at 0.05% as sole carbon source, whereas growth in the same conditions using xylan was confirmed.

Chitinases are produced by Metarhizium anisopliae when it is grown in the presence of chitin. A chitinase from the culture filtrate of Metarhizium anisopliae was successively purified by precipitation with ammonium sulphate, followed by anion-exchange chromatography on DEAE-Sephacel. The purified enzyme, which has a molecular mass of approximately 30 kDa by sodium dodecyl sulphate – polyacrylamide gel electrophoresis, catalyses the hydrolysis of p-nitrophenyl β-N-diacetylchitobiose with an apparent K_m of 0.537 mmol and V_max of 4.86 nmol∙mL⁻¹∙min⁻¹. The optimum pH and temperature were 4.5–5.0 and 40–45 °C, respectively.Key words: chitinases, Metarhizium anisopliae, enzyme purification, enzyme characterization.