Pasture degradation can cause changes in diazotrophic bacterial communities. Thus, this study aimed to evaluate the culturable and total diazotrophic bacterial community, associated with regions of the rhizosphere and roots of Brachiaria decumbens Stapf. pastures in different stages of degradation. Samples of roots and rhizospheric soil were collected from slightly, partially, and highly degraded pastures. McCrady's table was used to obtain the Most Probable Number (MPN) of bacteria per gram of sample, in order to determine population density and calculate the Shannon-Weaver diversity index. The diversity of total diazotrophic bacterial community was determined by the technique of Denaturing Gradient Gel Electrophoresis (DGGE) of the nif H gene, while the diversity of the culturable diazotrophic bacteria was determined by the Polymerase Chain Reaction (BOX-PCR) technique. The increase in the degradation stage of the B. decumbens Stapf. pasture did not reduce the population density of the cultivated diazotrophic bacterial community, suggesting that the degradation at any degree of severity was highly harmful to the bacteria. The structure of the total diazotrophic bacterial community associated with B. decumbens Stapf. was altered by the pasture degradation stage, suggesting a high adaptive capacity of the bacteria to altered environments.
Microbial strains isolated from extreme and understudied environments, such as caves, are still poorly investigated for the production of bioactive secondary metabolites. Investigation of the ethyl acetate extract from the growth medium produced by the soil-derived fungus Aspergillus sp. SDC28, isolated from a Brazilian cave, yielded two anthraquinones: versicolorin C (1) and versiconol (2). The complete assignment of nuclear magnetic resonance and mass spectroscopic data of 1 and 2 was performed for the first time. Moreover, the yet unreported absolute configuration of both compounds was unambiguously established by analysis of experimental and theoretical electronic circular dichroism data. Vibrational circular dichroism was also applied to confirm the absolute stereochemistry of 2. Compounds 1 and 2 showed cytotoxic activity against human ovarian cancer cells (OVCAR3).
IntroductionPhytopathogenic fungi are a considerable concern for agriculture, as they can threaten the productivity of several crops worldwide. Meanwhile, natural microbial products are acknowledged to play an important role in modern agriculture as they comprehend a safer alternative to synthetic pesticides. Bacterial strains from underexplored environments are a promising source of bioactive metabolites.MethodsWe applied the OSMAC (One Strain, Many Compounds) cultivation approach, in vitro bioassays, and metabolo-genomics analyses to investigate the biochemical potential of Pseudomonas sp. So3.2b, a strain isolated from Antarctica. Crude extracts from OSMAC were analyzed through HPLC-QTOF-MS/MS, molecular networking, and annotation. The antifungal potential of the extracts was confirmed against Rhizoctonia solani strains. Moreover, the whole-genome sequence was studied for biosynthetic gene clusters (BGCs) identification and phylogenetic comparison.Results and DiscussionMolecular networking revealed that metabolite synthesis has growth media specificity, and it was reflected in bioassays results against R. solani. Bananamides, rhamnolipids, and butenolides-like molecules were annotated from the metabolome, and chemical novelty was also suggested by several unidentified compounds. Additionally, genome mining confirmed a wide variety of BGCs present in this strain, with low to no similarity with known molecules. An NRPS-encoding BGC was identified as responsible for producing the banamides-like molecules, while phylogenetic analysis demonstrated a close relationship with other rhizosphere bacteria. Therefore, by combining -omics approaches and in vitro bioassays, our study demonstrates that Pseudomonas sp. So3.2b has potential application to agriculture as a source of bioactive metabolites.
This work highlighted a putative link between the physiological activity and genetic diversity of Methylobacterium species and the association with sugarcane roots and rhizoplane. In total, 40 isolates previously described as pink-pigmented facultative methylotrophic bacteria (PPFMs), were evaluated for their ability to fix nitrogen and solubilize inorganic phosphate, amylase and pectinase activity. This in vitro potential was positively correlated with the community isolated from the root tissues than those from the rhizoplane. Regarding the genomic fingerprinting, the (BOX-PCR) approach revealed a low similarity among the isolates, occurring sole 7 haplotypes harboring more than 70% of similarity among band patterns. These results revealed that the genomic fingerprinting of the isolates recovery from roots is different from the rhizoplane. Besides that, these haplotypes occurred on both sugarcane varieties. Using a phylogenetic sequencing approach based on the 16S rRNA gene, we observed a high abundance of sequences similar to Methylobacterium radiotolerans colonizing both plant tissue and sugarcane varieties were observed. Hence, it was suggested that the plant should select those Methylobacterium spp. with a high biotechnological potential to promote plant growth. Therefore, the bioprospection of specific endophytic bacterial groups comprise an important source of biotechnological potential to improve sugarcane growth and production.
Bioassay-guided investigation of the EtOAc-soluble extract of a culture of the marine-derived fungus Peroneutypa sp. M16 led to the isolation of seven new polyketide-and terpenoid-derived metabolites (1, 2, 4−8), along with known polyketides (3, 9−13). Structures of compounds 1, 2, and 4−8 were established by analysis of spectroscopic data. Absolute configurations of compounds 1, 2, 4, 6, 7, and 8 were determined by the comparison of experimental ECD spectra with calculated CD data. Compound 5 exhibited moderate antiplasmodial activity against both chloroquine-sensitive and -resistant strains of Plasmodium falciparum.
Tamires e Thaís. Aos meninos da casa 3, Antônio (Neto), Antônio Marcos (Tony) e Octávio, obrigada por todas as noites com café, biscoito e bolo, por todas as risadas durante o período "apertado" e noites em claro. Às meninas que são meu maior sinal de amizade, que me mostraram que ser amigo não tem a ver com tempo, mas com carinho, cuidado e reciprocidade, juntas formamos o "quarteto fantástico": Beatriz, Giovana e Letícia, amo vocês! Ao DVATCOM pela oportunidade de morar na Vila Estudantil da Pós-Graduação, às assistentes sociais Eliana e Solange, e à Maria das Graças. A todos os funcionários da ESALQ, às pessoas que fazem parte das secretarias, aos que fazem parte da biblioteca e aos funcionários das empresas terceirizadas, que se dedicam para garantir o bom funcionamento da instituição.
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