Biodiversity underlies ecosystem functioning. While aboveground biodiversity is often well studied, the belowground microbiome, in particular protists, remains largely unknown. Indeed, holistic insights into soil microbiome structures in natural soils, especially in hyperdiverse biomes such as the Brazilian Cerrado, remain unexplored. Here, we study the soil microbiome across four major vegetation zones of the Cerrado, ranging from grass-dominated to tree-dominated vegetation with a focus on protists. We show that protist taxon richness increases towards the tree-dominated climax vegetation. Early successional habitats consisting of primary grass vegetation host most potential plant pathogens and least animal parasites. Using network analyses combining protist with prokaryotic and fungal sequences, we show that microbiome complexity increases towards climax vegetation. Together, this suggests that protists are key microbiome components and that vegetation succession towards climax vegetation is stimulated by higher loads of animal and plant pathogens. At the same time, an increase in microbiome complexity towards climax vegetation might enhance system stability.

Phylogenetic analyses, from polymerase chain reaction (PCR)-amplified 12S rRNA and 18S rRNA gene sequences from cochineal insects of the genus Dactyl

Strain SVQ121 is a mutant derivative of Sinorhizobium fredii HH103 carrying a transposon Tn5-lacZ insertion into the nolO-coding region. Sequence analysis of the wild-type gene revealed that it is homologous to that of Rhizobium sp. NGR234, which is involved in the 3 (or 4)-O-carbamoylation of the nonreducing terminus of Nod factors. Downstream of nolO, as in Rhizobium sp. NGR234, the noeI gene responsible for methylation of the fucose moiety of Nod factors was found. SVQ121 Nod factors showed lower levels of methylation into the fucosyl residue than those of HH103-suggesting a polar effect of the transposon insertion into nolO over the noel gene. A noeI HH103 mutant was constructed. This mutant, SVQ503, produced Nod factors devoid of methyl groups, confirming that the S. fredii noeI gene is functional. Neither the nolO nor the noeI mutation affected the ability of HH103 to nodulate several host plants, but both mutations reduced competitiveness to nodulate soybean. The Nod factors produced by strain HH103, like those of other S. fredii isolates, lack carbamoyl residues. By using specific polymerase chain reaction primers, we sequenced the nolO gene of S. fredii strains USDA192, USDA193, USDA257, and 042B(s). All the analyzed strains showed the same -1 frameshift mutation that is present in the HH103 nolO-coding region. From these results, it is concluded that, regardless of their geographical origin, S. fredii strains carry the nolO-coding region but that it is truncated by the same base-pair deletion.

The preserved Cerrado from Northeastern Brazil presents different physicochemical properties and plant diversity, which can influence the fungal communities. Therefore, we evaluated the fungal diversity in preserved sites, at Sete Cidades National Park, across a gradient of vegetation that included Campo graminoide, Cerrado stricto sensu, Cerradao, and Floresta decidual. Of all of the operational taxonomic units (OTUs) obtained, the Floresta decidual presented the highest richness. Ascomycota were the most abundant phylum (45%), followed by Basidiomycota (32%). Basal fungi and other phyla accounted for 23% of the total dataset. Agaricomycetes, Eurotiomycetes, Lecanoromycetes, Basidiobolus, Dothideomycetes, and Taphrinomycetes were the most abundant classes of fungi found across the gradient of Cerrado vegetation. In conclusion, our study suggests that the Brazilian Cerrado from Sete Cidades National Park presents a high fungal diversity and includes sources of new fungal species for biotechnological purposes.

Pesquisas sobre a biodiversidade microbiológica de solos salinos envolvem a busca por genótipos tolerantes a esse tipo de estresse ambiental. Dados genotípicos correlacionados às características morfológicas, fisiológicas e bioquímicas de bactérias fornecem informações importantes para sua identificação e agrupamento. Este trabalho objetivou caracterizar rizóbios provenientes de solos salinos, do Agreste e Sertão de Pernambuco, utilizando jacatupé (Pachyrhizus erosus L. Urban) como planta-isca. Os testes foram efetuados em meio YMA e as características culturais observadas em 24 isolados foram as seguintes: mudança de pH, tempo de crescimento, transparência, forma, borda, produção de exopolissacarídeo das colônias e resistência à salinidade. Os testes moleculares utilizando análise por PCR (reação em cadeia da polimerase) por meio de seqüências repetitivas de DNA amplificadas com o primer BOX envolveram 13 isolados. Os resultados revelaram alta diversidade fenotípica e genotípica entre os isolados nativos. As características culturais e genéticas desses isolados foram comparados com 19 estirpes de referência. Os isolados NFB746 e NFB747 tiveram alta semelhança entre si e também com as estirpes Rhizobium sp. NGR234 (BR2406) e Mesorhizobium ciceri USDA3383 (BR521). O isolado NFB742, possivelmente, era da mesma espécie de M. ciceri (BR521). Com relação ao isolado NFB741, a semelhança com as bactérias Rhizobium tropici IIA CFN299T (BR10016) e Sinorhizobium terangue USDA4894 (BR527) foi de 87%. Os demais isolados, praticamente, formaram grupos independentes quando comparados com as estirpes de referência. Os resultados foram de grande relevância para diagnosticar novas espécies de rizóbios nativos altamente tolerantes a estresses ambientais.