The molecular mechanisms of plant recognition, colonization, and nutrient exchange between diazotrophic endophytes and plants are scarcely known. Herbaspirillum seropedicae is an endophytic bacterium capable of colonizing intercellular spaces of grasses such as rice and sugar cane. The genome of H. seropedicae strain SmR1 was sequenced and annotated by The Paraná State Genome Programme—GENOPAR. The genome is composed of a circular chromosome of 5,513,887 bp and contains a total of 4,804 genes. The genome sequence revealed that H. seropedicae is a highly versatile microorganism with capacity to metabolize a wide range of carbon and nitrogen sources and with possession of four distinct terminal oxidases. The genome contains a multitude of protein secretion systems, including type I, type II, type III, type V, and type VI secretion systems, and type IV pili, suggesting a high potential to interact with host plants. H. seropedicae is able to synthesize indole acetic acid as reflected by the four IAA biosynthetic pathways present. A gene coding for ACC deaminase, which may be involved in modulating the associated plant ethylene-signaling pathway, is also present. Genes for hemagglutinins/hemolysins/adhesins were found and may play a role in plant cell surface adhesion. These features may endow H. seropedicae with the ability to establish an endophytic life-style in a large number of plant species. In this work we describe the genome of H. seropedicae SmR1, a bacterium capable of fixing nitrogen and promoting the growth of important plant crops such as maize, rice, and sugar cane. Several investigations have shown that H. seropedicae supplies fixed nitrogen to the associated plant and increases grain productivity up to 50%. In the genome of H. seropedicae, we identified all the genes involved in the nitrogen fixation process and its regulation and, in addition, genes potentially involved in the establishment of efficient interaction with the host plant. Our analyses also revealed that this bacterium has a highly versatile metabolism capable of synthesizing and degrading a large number of organic and inorganic compounds. We believe that the knowledge of the genome of this bacterium will direct research to a better understanding of this important endophytic organism and allow the construction of new strains with enhanced agronomic efficiency.

We studied the expression of DnaK and GroEL in Acinetobacter baumannii cells (strains ATCC 19606 and RS4) under stress caused by heat shock or antibiotics. A Western blot assay showed that DnaK and GroEL levels increased transiently more than 2-fold after exposure of bacterial cells to heat shock for 20 min at 50 °C. Heat induction of DnaK and GroEL was blocked completely when an inhibitor of transcription, rifampicin, was added 1 min before a temperature upshift to 50 °C, suggesting that the induction of these chaperones depends on transcription. A. baumannii cells pretreated at 45 °C for 30 min were better able to survive at 50 °C for 60 min than cells pretreated at 37 °C, indicating that A. baumannii is able to acquire thermotolerance. DnaK and GroEL were successfully induced in cells pre-incubated with a subinhibitory concentration of streptomycin. Moreover, bacterial cells pretreated for 30 min at 45 °C were better able to survive streptomycin exposure than cells pretreated at physiological temperatures. DnaK expression was upregulated in a multidrug-resistant strain of A. baumannii (RS4) in the presence of different antimicrobials (ampicillin+sulbactam, cefepime, meropenem and sulphamethoxazole+trimethoprim). This study is to the best of our knowledge the first to show that A. baumannii DnaK and GroEL could play an important role in the stress response induced by antibiotics.

The world practice of using agrochemicals for long periods, in an indiscriminated and abusive way, has been a concern of the authorities involved in public health and sustainability of the natural resources, as a consequence of environmental contamination. Agrochemicals refer to a broad range of insecticides, fungicides and herbicides, and among them stands out atrazine, a herbicide intensively used in sugarcane, corn and sorghum cultures, among others. Researches have demonstrated that atrazine has toxic effects in algae, aquatic plants, aquatic insects, fishes and mammals. Due to the toxicity and persistence of atrazine in the environment, the search of microbial strains capable of degrading it is fundamental to the development of bioremediation processes, as corrective tools to solve the current problems of the irrational use of agrochemicals. This review relates the main microbial aspects and research on atrazine degradation by isolated microbial species and microbial consortia, as well as approaches on the development of techniques for microbial removal of atrazine in natural environments.