RESUMO
Paenibacillus elgii AC13 produces antimicrobial lipopeptides of agricultural and pharmaceutical importance. It secretes four cyclic lipopeptides named pelgipeptins, previously characterized in P. elgii B69. These lipopeptides result from the expression of a nonribosomal peptide gene cluster. P. elgii AC13 also produced two linear lipopeptides with ratios of [M + H] + 1105 and 1119 m/z. These compounds were previously observed in Paenibacillus sp. strain OSY-N, but due to purification difficulties, their characterization was executed using synthetically produced linear pelgipeptins. In the present study, purification was achieved from the supernatants of cultures from three complex media by high-performance liquid chromatography. The partial characterization of linear pelgipeptins revealed the similar antimicrobial activity and cytotoxicity of their synthetically produced counterparts, known as paenipeptins. Cyclic forms were highly stable to changes in pH, temperature, and organic extraction with n-butanol as shown by mass spectrometry (MALDI-TOF); therefore, these steps did not cause the hydrolysis of pelgipeptins. A low-activity thioesterase could also generate the linear isoforms observed; this enzyme catalyzes the cyclization process and is coded in the same gene cluster. Alternatively, the cyclic forms were hydrolyzed by an unknown protease produced during growth in the complex medium used in the present study. Although culture conditions are known to produce pelgipeptins with different yields and amino acid compositions, the occurrence of linear and cyclic forms simultaneously has not yet been reported. A mixture of cyclic and linear pelgipeptins presents a potential advantage of the higher antimicrobial activity of cyclic forms combined with the lower cytotoxicity of linear isoforms.
Assuntos
Lipopeptídeos , Paenibacillus , Anti-Infecciosos/química , Anti-Infecciosos/isolamento & purificação , Anti-Infecciosos/farmacologia , Bactérias/efeitos dos fármacos , Lipopeptídeos/química , Lipopeptídeos/genética , Lipopeptídeos/isolamento & purificação , Lipopeptídeos/farmacologia , Paenibacillus/química , Paenibacillus/genéticaRESUMO
Metagenomic studies revealed the prevalence of Acidobacteria in soils, but the physiological and ecological reasons for their success are not well understood. Many Acidobacteria exhibit carotenoid-related pigments, which may be involved in their tolerance of environmental stress. The aim of this work was to investigate the role of the orange pigments produced by Acidobacteria strain AB23 isolated from a savannah-like soil and to identify putative carotenoid genes in Acidobacteria genomes. Phylogenetic analysis revealed that strain AB23 belongs to the Occallatibacter genus from the class Acidobacteriia (subdivision 1). Strain AB23 produced carotenoids in the presence of light and vitamins; however, the growth rate and biomass decreased when cells were exposed to light. The presence of carotenoids resulted in tolerance to hydrogen peroxide. Comparative genomics revealed that all members of Acidobacteriia with available genomes possess the complete gene cluster for phytoene production. Some Acidobacteriia members have an additional gene cluster that may be involved in the production of colored carotenoids. Both colored and colorless carotenoids are involved in tolerance to oxidative stress. These results show that the presence of carotenoid genes is widespread among Acidobacteriia. Light and atmospheric oxygen stimulate carotenoid synthesis, but there are other natural sources of oxidative stress in soils. Tolerance to environmental oxidative stress provided by carotenoids may offer a competitive advantage for Acidobacteria in soils.
Assuntos
Acidobacteria/genética , Acidobacteria/metabolismo , Farmacorresistência Bacteriana/genética , Peróxido de Hidrogênio/toxicidade , Estresse Oxidativo/fisiologia , Acidobacteria/efeitos dos fármacos , Acidobacteria/isolamento & purificação , Carotenoides/metabolismo , DNA Bacteriano/genética , Genoma Bacteriano/genética , Família Multigênica/genética , Solo/química , Microbiologia do SoloRESUMO
Serpentine soils present unique characteristics such as a low Ca/Mg ratio, low concentration of nutrients, and a high concentration of heavy metals, especially nickel. Soil bacterial isolates from an ultramafic complex located in the tropical savanna known as the Brazilian Cerrado were studied. Nickel-tolerant bacteria were obtained, and their ability to remove nickel from a culture medium was assessed. Bacterial isolates presented higher tolerance to nickel salts than previously reported for bacteria obtained from serpentine environments in other regions of the world. In addition, the quantification of nickel in cell pellets indicated that at least four isolates may adsorb soluble forms of nickel. It is expected that information gathered in this study will support future efforts to exploit serpentine soil bacteria for biotechnological processes involving nickel decontamination from environmental samples.
Assuntos
Bactérias/metabolismo , Níquel/metabolismo , Alcaloides de Triptamina e Secologanina/análise , Microbiologia do Solo , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , Brasil , Filogenia , Alcaloides de Triptamina e Secologanina/metabolismo , Solo/químicaRESUMO
Bacteria from the Mucilaginibacter genus are still poorly understood, although their importance has been shown by recent reports describing great quantities of biofilms produced in their colonies. We report the draft genome sequence of a novel Mucilaginibacter member, comprising 8 contigs, totaling 5,478,589 bp and 4,876 predicted coding sequences.
RESUMO
The granular glands of anuran skin secrete an array of bioactive molecules that protect a frog against pathogens and predators. The skin also harbors a microbial community. Although there is evidence to suggest that the microbiota complement the innate immune defense systems against pathogen infection, the effect of the frog bioactive molecules on its resident microbiota has not yet been fully investigated. In the present study, the skin microbiota of Phyllomedusa distincta obtained from two different geographical areas was evaluated with molecular and culture-based approaches. The antagonistic effects exhibited by the host's microbiota and by a novel dermaseptin peptide isolated from P. distincta skin were investigated. Four isolated bacterial colonies displayed antimicrobial activity against known frog pathogens. Our results were consistent with the hypothesis that microbiota from P. distincta may interact with pathogenic microorganisms to protect a frog's health. On the other hand, the novel dermaseptin peptide exhibited an antimicrobial effect on pathogens as well as on some of the bacteria obtained from the skin microbiota. The richness of bacteria on P. distincta skin was further investigated by 16S rRNA gene clone libraries, which revealed that the family Enterobacteriaceae was prevalent, but a high variability at the species level was observed among individual frogs. Differences observed on the microbiota of frogs from contrasting habitats indicated an influence of the environment on the structure of the skin microbiota of P. distincta.
Assuntos
Antibacterianos/farmacologia , Anuros , Microbiota , Pele/química , Sequência de Aminoácidos , Animais , Sequência de Bases , Homologia de Sequência de Aminoácidos , Pele/microbiologiaRESUMO
Ultramafic soils are characterized by high levels of metals, and have been studied because of their geochemistry and its relation to their biological component. This study evaluated soil microbiological functioning (SMF), richness, diversity, and structure of bacterial communities from two ultramafic soils and from a non-ultramafic soil in the Brazilian Cerrado, a tropical savanna. SMF was represented according to simultaneous analysis of microbial biomass C (MBC) and activities of the enzymes ß-glucosidase, acid phosphomonoesterase and arylsulfatase, linked to the C, P and S cycles. Bacterial community diversity and structure were studied by sequencing of 16S rRNA gene clone libraries. MBC and enzyme activities were not affected by high Ni contents. Changes in SMF were more related to the organic matter content of soils (SOM) than to their available Ni. Phylogeny-based methods detected qualitative and quantitative differences in pairwise comparisons of bacterial community structures of the three sites. However, no correlations between community structure differences and SOM or SMF were detected. We believe this work presents benchmark information on SMF, diversity, and structure of bacterial communities for a unique type of environment within the Cerrado biome.
Assuntos
Bactérias/classificação , Bactérias/isolamento & purificação , Biota , Microbiologia do Solo , Arilsulfatases/análise , Bactérias/genética , Bactérias/crescimento & desenvolvimento , Biomassa , Brasil , Análise por Conglomerados , DNA Ribossômico/química , DNA Ribossômico/genética , Pradaria , Dados de Sequência Molecular , Monoéster Fosfórico Hidrolases/análise , Filogenia , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Clima Tropical , beta-Glucosidase/análiseRESUMO
O meloeiro tem reconhecida importância sócio-econômica no Nordeste do Brasil, porém a falta ou excesso de água limita o seu cultivo. Para tanto, é necessário determinar a quantidade ideal para a obtenção do máximo rendimento. Assim, objetivou-se avaliar a eficiência fotoquímica e o rendimento do meloeiro Cantaloupe sob diferentes lâminas de irrigação. O trabalho foi conduzido em condições de campo, adotando-se o delineamento em blocos ao acaso com 4 tratamentos [(60; 80; 100 e 120% da ETo (mm dia-¹)] que corresponderam aos volumes de água acumulados de 1250, 1680, 2110 e 2540 m3ciclo -¹, respectivamente; e 6 repetições com 10 plantas úteis por parcela. Analisaram-se as variáveis: fluorescência da clorofila a, rendimento e atributos físico-químicos dos frutos. A lâmina de água de 80% da ETo promoveu maior eficiência do fotossistema II. Houve menor produção de frutos da Classe I na lâmina superior a 100% da ETo; a incidência de frutos das Classes II e III cresceu linearmente com o aumento das lâminas de água. O tamanho dos frutos foi reduzido com irrigações superiores a 100% da ETo; no entanto, o teor de açúcar foi satisfatório até irrigações com 80% da ETo. Lâminas de água baseadas em 100% da ETo proporcionam os melhores índices fisiológicos e incrementos nas variáveis de produção.
The melon crop has great social and economic importance to Northeastern Brazil, however, lack and excess of water affect growth. Therefore it is necessary to determine ideal water amount to obtain the maximum yield. This research work aimed to evaluate photochemical efficiency and yield of Cantaloupe melon under different irrigations levels. The work was carried in field conditions, adopting a randomized block design with 4 treatments [(60, 80, 100, and 120% of ET0 (mm day-1) corresponded to the volume of water accumulated during the cycle: 1250, 1680, 2110 and 2540 m3 cycle-1, respectively, and 6 replications with 10 plants per experimental unit. The following variables were analyzed: chlorophyll fluorescence, yield and physical and chemical attributes fruits. The 80% ETo water level provided the higher efficiency of Photosystem II. There was lower production of Class I fruits with the level irrigation higher than 100% ETo; and the incidence of the class II and III fruits increased linearly with increasing water levels. There was a reduction in fruit size with irrigation higher than 100% ETo, however the sugar content was satisfactory with irrigation up to 80% ETo. Water levels based on 100% ETo provide the best physiological indices and increasing in production variables.