Draft Genome Sequence of Achromobacter sp. Strain AR476-2, Isolated from a Cellulolytic Consortium

The difference between cellulolytic 'culturomes' and microbiomes inhabiting two contrasting soil types

High-throughput 16S rRNA sequencing was performed to compare the microbiomes inhabiting two contrasting soil types-sod-podzolic soil and chernozem-and the corresponding culturome communities of potentially cellulolytic bacteria cultured on standard Hutchinson media. For each soil type, soil-specific microorganisms have been identified: for sod-podzolic soil-Acidothermus, Devosia, Phenylobacterium and Tumebacillus, and for chernozem soil-Sphingomonas, Bacillus and Blastococcus. The dynamics of differences between soil types for bulk soil samples and culturomes varied depending on the taxonomic level of the corresponding phylotypes. At high taxonomic levels, the number of common taxa between soil types increased more slowly for bulk soil than for culturome. Differences between soil-specific phylotypes were detected in bulk soil at a low taxonomic level (genus, species). A total of 13 phylotypes were represented both in soil and in culturome. No relationship was shown between the abundance of these phylotypes in soil and culturome.

Dynamics of Abundant and Rare Bacteria During Degradation of Lignocellulose from Sugarcane Biomass

Microorganisms play a crucial role in lignocellulosic degradation. Many enriched microbial communities have demonstrated to reach functional and structural stability with effective degrading capacities of industrial interest. These microbial communities are typically composed by only few dominant species and a high number of usually overlooked rare species. Here, we used two sources of lignocellulose (sugarcane bagasse and straw) in order to obtain lignocellulose-degrading bacteria through an enriched process, followed the selective trajectory of both abundant and rare bacterial communities by 16S rRNA gene amplification and analyzed the outcomes of selection in terms of capacities and specialization. We verified the importance of pre-selection by using two sources of microbial inoculum: soil samples from a sugarcane field with history of straw addition (St15) and control samples, from the same field, without amendments (St0). We found similitudes in terms of stabilization between the abundant and rare fractions. We also found positive correlations of both abundant and rare taxa (like Caulobacteraceae and Alcaligenaceae) and the degradation of lignocellulosic fractions. Differences in the inocula's initial diversity rapidly decreased during the enrichment resulting in comparable richness levels at the end of the process; however, the legacy of the St15 inoculum and its specialization positively influenced the degradation capacities of the community. Analysis of specialization of the final communities revealed increased straw degradation capacity in the communities enriched in bagasse, which could be potentially used as a strategy for improving lignocellulose waste degradation on the sugarcane fields. This work highlights the importance of including the rare fraction of bacterial communities during investigations involving the screening and assessment of effective degrading communities.

Endoglucanase and xylanase production by Bacillus sp. AR03 in co-culture

The behavior of three isolates retrieved from different cellulolytic consortia, Bacillus sp. AR03, Paenibacillus sp. AR247 and Achromobacter sp. AR476-2, were examined individually and as co-cultures in order to evaluate their ability to produce extracellular cellulases and xylanases. Utilizing a peptone-based medium supplemented with carboxymethyl cellulose (CMC), an increase estimation of 1.30 and 1.50 times was obtained by the co-culture containing the strains AR03 and AR247, with respect to enzyme titles registered by their individual cultivation. On the contrary, the extracellular enzymatic production decreased during the co-cultivation of strain AR03 with the non-cellulolytic Achromobacter sp. AR476-2. The synergistic behavior observed through the combined cultivation of the strains AR03 and AR247 might be a consequence of the consumption by Paenibacillus sp. AR247 of the products of the CMC hydrolysis (i.e., cellobiose and/or cello-oligosaccharides), which were mostly generated by the cellulase producer Bacillus sp. AR03. The effect observed could be driven by the requirement to fulfill the nutritional supply from both strains on the substrate evaluated. These results would contribute to a better description of the degradation of the cellulose fraction of the plant cell walls in nature, expected to an efficient utilization of renewable sources.