FROM TIME TO TIME THE SAME QUESTIONS:"WHO"ARE RHIZOBIA?, WHAT DO THEY DO?, HOW ACTIVELY THEY. EVOLVE? STATIC PICTURES FROM MOVING GENOMES?

LAGARES, A.; DEL PAPA, M.F.; PISTORIO, M.; DRAGHI, W.O.; LOZANO, M.J.; GIUSTI, M.A.; TORRES TEJERIZO, G.A.; SALAS, M.E.

Mar del Plata

Congreso; VIII Congreso de Microbiología General; 2012

Sociedad Argentina de Microbiología General

Bacteria colonize quite diverse environments and are well recognized by their remarkablecapacity to sense, adapt, and respond to different (and in cases challenging) extracellularconditions. While cells in multicellular organisms evolved to perform specific functions undercarefully controlled conditions (homeostasis), bacteria -as unicellular organisms- learned on howto live most of their life time under changing and frequently contrasting environments. For thesereasons, bacteria represent valuable systems to investigate strategies of short and long termprocesses of adaptation. In this context of analysis, bacteria with both free- and associative-styleof life provide extraordinary possibilities to investigate how cells cyclically accommodate tocontrasting extracellular conditions.In our laboratory we study since more than two decades the biology and biochemistry of rhizobia;gram negative bacteria that live in the underground and associate with the roots of legumeswhere they fix atmospheric nitrogen receiving and, in turn, use photosynthetic carbon. We willpresent -with their pros and cons- classical and modern experimental approaches to characterizeadaptive responses of rhizobia to stressing environments. We will discuss what we learned ontransient adaptive responses to stress, how they affect the free living and the symbiosis, and thepossibilities to explore their practical use for a better formulation of biofertilizers.Finally, we will discuss the use of genome-wide comparative genomic analyses to investigatelong-term changes in rhizobia, and their associated behavioral consequences. We will analyzethe general mechanisms that model rhizobial diversification, and show how they are evident withdata that we collected from the analysis of chromosomes and plasmids (sym and cryptic) in theMedicago spp.-nodulating rhizobia.Evidences currently available on the rhizobial genomics will be discussed to help the audiencethinking on the identity and diversity of the legume nodulating bacteria.