Isolation and Characterization of Plant Growth-Promotion Diazotrophic Endophytic Bacteria Associated to Sugarcane (Saccharum officinarum L.) Grown in Paraíba, Brazil

Abstract: Sugarcane is an important Brazilian commodity, being usually cultivated in soils with low natural fertility. This study aimed to isolate diazotrophic endophytes from sugarcane tissues and evaluate the morphological and physiological characteristics of their colonies as well as their plant growth-promoting (PGP) traits in select diazotrophic endophytic bacteria. Fifty-six bacterial isolates were identified in the sugarcane tissues, and these isolates presented distinct morphological and physiological traits. A total of thirty-five bacterial isolates were biochemically evaluated. Overall, Bacillus was the dominant genus. Isolates of Methylobacterium spp. and Brevibacillus agri were present only in leaves, while Herbaspirillum seropedicae occurred only in stems. Except to IPA-CF45A, all isolates were nitrogenase positive. All endophytes exhibit production of indol 3-acetic acid. Over 50% of endophytes solubilize phosphate, release N-acyl homoserine lactones, and present the activity of 1-aminocyclopropane-1-carboxylic acid deaminase, catalase, lipase and protease. The network analysis showed that isolates belonged to Burkholderia, Herbaspirillum, and Methylobacterium interact with Bacillus. Bacterial endophytes exhibited distinct morphological, physiological, and PGP traits that are useful for sustainable agriculture, highlighting the isolates IPA-CC33, IPA-CF65, IPA-CC9 and IPA-CF27. Further studies on the effects of these diazotrophic endophytes and their potential for providing microbial inoculants for improving sugarcane fields will provide valuable information to maintain the sustainability and environment quality.

Archaea diversity in vegetation gradients from the Brazilian Cerrado

Abstract We used 16S rRNA sequencing to assess the archaeal communities across a gradient of Cerrado. The archaeal communities differed across the gradient. Crenarcheota was the most abundant phyla, with Nitrosphaerales and NRPJ as the predominant classes. Euryachaeota was also found across the Cerrado gradient, including the classes Metanocellales and Methanomassiliicoccaceae.

Archaea diversity in vegetation gradients from the Brazilian Cerrado.

We used 16S rRNA sequencing to assess the archaeal communities across a gradient of Cerrado. The archaeal communities differed across the gradient. Crenarcheota was the most abundant phyla, with Nitrosphaerales and NRPJ as the predominant classes. Euryachaeota was also found across the Cerrado gradient, including the classes Metanocellales and Methanomassiliicoccaceae.

Identificação de bactérias diazotróficas isoladas em cultivares de palma (Opuntia e Nopalea) usando o gene recA / Identification of diazotrophs isolated from palm cultivars (Opuntia and Nopalea) using the recA gene

Este trabalho teve como objetivo caracterizar filogeneticamente os isolados bacterianos da cultura da palma forrageira usando o gene recA. Para o isolamento caldódios de palma foram maceradas e inoculadas em meios semissólido semi-seletivo NFb, JNFb, LGI e LG sem adição de nitrogênio. Foram obtidos doze micro-organismos cuja a analise parcial do gene recA possibilitou a identificação dos gêneros Azospirillum, Bacillus e Methylobacterium.. Bactérias diazotróficas encontrados na cultura da palma podem ter uma grande função como bactéria promotora de crescimento. O gene recA mostrou-se bastante consistente para uso em filogenia molecular de bactérias. Observou-se ainda a presença de bactérias destes gêneros podem ter de grande interesse para futuros estudos considerando seu alto poder biotecnológico.

This study aimed to characterize phylogenetically isolated bacterial culture of Cactus Pear using the parcial gene recA. For isolation cladodes were macerated and inoculated in semi-selective semisolid media NFB, JNFb, LGI and LG without added nitrogen. Twelve micro-organisms were obtained whose analysis of partial gene recA enabled the identification of the genera Azospirillum, Bacillus and Methylobacterium. Diazotrophic bacteria found in the culture of Cactus Pear may have a great function as growth-promoting bacteria. The partial gene recA was shown to be quite consistent for use in molecular phylogeny of bacteria. We also observed the presence of bacteria of these genera may be of great interest for future studies considering its high power biotechnology.

Nitrate levels and stages of growth in hypernodulating mutants pf Lupinus Albus. I. N2 fixation potential

This work aimed to evaluate physiological parameters, nodulation response and N2 fixation rate in mutants of Lupinus albus in comparison with the standard Multolupa cultivar. Two nitrate levels (0 and 5mM) and two evaluation periods (7 and 10 weeks) were used. Significant differences were observed among genotypes, in relation to fresh nodule weight, nitrate levels and growth stages. The overall average for nitrate level differed between them where 5mM severely inhibieted the number of nodules, reaching a 49.5 (per cent) reduction in relation to treatment without nitrate. There were no behaviour differences among genotypes, nor among evaluation periods. Although the level of nitrate did not influence the production of shoot dry matter in relation to the average among levels applied, the L-135 genotype, being an inefficient mutant, reached very low values. There were no significant differences in electron allocation coefficient (EAC) among nitrate levels, nor among genotypes studied. However , the evaluation periods revealed differences, where the EAC for the seventh week had a higher value than that for the tenth week, when a 5mM aplication was evaluated. The N2 fixation rate (N2FIX) showed the existence of the nitrate interference in fixation, given that the application of 5mM severely reduced. However, there were no differences among the genotypes and it was noted that the fixation rate was much higher in those that received nitrate. The L-88 and L-62 genotypes were the ones that have shown best adaptability in this experiment, thus being able to be recommended for new studies with higher nitrate levels and different evaluation periods. The nitrate (5mM) interferes in the nitrogen fixation rate, given that all the genotypes were affected by the level applied.

Nitrate levels and stages of growth in hypernodulating mutants of Lupinus Albus. II.Enzymatic activity and transport of N in the xylem SAP

The enzymatic study and transport of N in the xylem sap was carried out with a view to observing the influence of different nitrate levels and growth stages of the plant in chemically treated mutants of Lupinus albus. Several stresses induce a reduction in plant growth, resulting in the accumulation of free amino acids, amides or ureides, not only in the shoot, but also in the roots and nodules. Although enzyme activity is decisive in avoiding products that inhibit nitrogenase by ammonium, little is known about the mechanism by wich the xylem carries these products. However, this process may be the key to the function of avoiding the accumulation of amino acids in the cells of infected nodules. The behaviour of the enzymes nitrate reductase (NR), phosphoenolpyruvate carboxylase (PEPC), glutamine synthetase (GS) and nitrogen compounds derived from fixation, such as N-Ó-amino, N-ureides and N-amide in mutant genotypes were observed. The NR enzyme was highly influenced by the application of nitrate showing much higher values than those in the non-application of nitrate, independently of genotype, being that the NR, the best evaluation period was in the tenth week. The L-62 genotype characterized with nitrate-resistance, clearly showed that the enzyme PEPC is inhibited by presence of nitrate. The L-135 genotype (nor fix) showed GS activity extremely low, thus demonstrating that GS is an enzyme highly correlated with fixation. With regard to the best growth stage for GS, Lupinus albus should be evaluated in the seventh week.

Effect of nitrate on nodulation and n2-fixation of lupinus mutabilis mutants at different growth stages

Uma das principais técnicas usadas para estudar o efeito inibidor do NO3 na fixaçäo biológica do N2, tem sido o uso de mutantes de estirpes de Rhizobium ou de plantas hospedeiras que näo apresentam o padräo usual de nodulaçäo. Este estudo foi conduzido usando genótipos parentais e mutantes de Lupinus mutabilis, submetidos a dois níveis de NO3: 0 e 5mM, com duas épocas de colheita: sete e dez semanas após emergência. A concentraçäo de 5mM revelou-se da maior importância na inibiçäo da nodulaçäo inicial de Lupinus, apesar de os dados demonstrarem que os mutantes L-114 e L-105 foram mais eficientes quanto a nodulaçäo, N-total e atividade da nitrogenase que a cv. SCG-25, e podem permitir um aumento da fixaçäo de N2. Mas näo houve diferenças na atividade da glutamina sintetase (GS) dos nódulos entre os mutantes L-114, L-105 e a cv. SCG-25, quando as plantas näo receberam NO3, mas na presença de NO3 houve tendência para os mutantes, especialmente para os L-114, apresentarem maior atividade de GS. Isto indica que o mutante L-114 tem uma maior capacidade de assimilaçäo do N fixado, associada com um maior suprimento de carboidratos disponíveis, como indicado pela atividade da PEP-carboxilase. Portanto, a tolerância parcial ao NO3 apresentada pelos mutantes L-114 e L-105 está associada com o fenótipo hipernodulante. Esta sugestäo pode ser observada de reduçäo de acetileno, que foram maiores para o mutante L-114 que para a cv. SCG-25, na presença ou na ausência de NO3