A consolidated analysis of the physiologic and molecular responses induced under acid stress in the legume-symbiont model-soil bacterium Sinorhizobium meliloti.

Abiotic stresses in general and extracellular acidity in particular disturb and limit nitrogen-fixing symbioses between rhizobia and their host legumes. Except for valuable molecular-biological studies on different rhizobia, no consolidated models have been formulated to describe the central physiologic changes that occur in acid-stressed bacteria. We present here an integrated analysis entailing the main cultural, metabolic, and molecular responses of the model bacterium Sinorhizobium meliloti growing under controlled acid stress in a chemostat. A stepwise extracellular acidification of the culture medium had indicated that S. meliloti stopped growing at ca. pH 6.0-6.1. Under such stress the rhizobia increased the O2 consumption per cell by more than 5-fold. This phenotype, together with an increase in the transcripts for several membrane cytochromes, entails a higher aerobic-respiration rate in the acid-stressed rhizobia. Multivariate analysis of global metabolome data served to unequivocally correlate specific-metabolite profiles with the extracellular pH, showing that at low pH the pentose-phosphate pathway exhibited increases in several transcripts, enzymes, and metabolites. Further analyses should be focused on the time course of the observed changes, its associated intracellular signaling, and on the comparison with the changes that operate during the sub lethal acid-adaptive response (ATR) in rhizobia.

First molecular detection of co-infection of honey bee viruses in asymptomatic Bombus atratus in South America / Primeira detecção molecular de co-infecção de vírus de abelhas em Bombus atratus assintomática na América do Sul

Pollination is critical for food production and has the particularity of linking natural ecosystems with agricultural production systems. Recently, losses of bumblebee species have been reported worldwide. In this study, samples from a commercial exploitation of bumblebees of Argentina with a recent history of deaths were studied using a multiplex PCR for the detection of the honey bee viruses most frequently detected in South America. All samples analysed were positive for co-infections with Deformed wing virus, Black queen cell virus and Sacbrood virus. This is the first report of infection of Bombus atratus with honey bee viruses. A better understanding of viral infections in bumblebees and of the epidemiology of viruses could be of great importance as bumblebees can serve as possible viral reservoirs, resulting in pathogen spillover towards honey bees and native bumblebees.

A polinização é essencial para a produção de alimentos e tem como particularidade a conexão entre os ecossistemas naturais com sistemas de produção agrícola. Recentemente, as perdas de espécies de bumblebee em todo o mundo têm sido relatadas. Neste trabalho, amostras de uma exploração comercial de bumblebee da Argentina, com recente história de mortes foram estudadas utilizando uma Multiplex PCR para a detecção de vírus de abelha mais frequentemente detectados na América do Sul. Todas as amostras analisadas foram positivas para as co-infecções com Deformed wing virus, Black queen cell viruses e Sacbrood virus. Este trabalho descreve o primeiro relato de infecção de Bombus atratus com vírus de abelhas. Uma melhor compreensão das infecções virais em bumblebee e da epidemiologia dos vírus poderia ser de grande importância, uma vez que tais abelhas podem servir como reservatório viral, com possível repercussão tanto na produtividade de abelhas melíferas como afetando-as diretamente.

First molecular detection of co-infection of honey bee viruses in asymptomatic Bombus atratus in South America.

Pollination is critical for food production and has the particularity of linking natural ecosystems with agricultural production systems. Recently, losses of bumblebee species have been reported worldwide. In this study, samples from a commercial exploitation of bumblebees of Argentina with a recent history of deaths were studied using a multiplex PCR for the detection of the honey bee viruses most frequently detected in South America. All samples analysed were positive for co-infections with Deformed wing virus, Black queen cell virus and Sacbrood virus. This is the first report of infection of Bombus atratus with honey bee viruses. A better understanding of viral infections in bumblebees and of the epidemiology of viruses could be of great importance as bumblebees can serve as possible viral reservoirs, resulting in pathogen spillover towards honey bees and native bumblebees.