CGPA IS REQUIRED FOR LAG-LOGPHASE TRANSITION ATLOWTEMPERATURESIN Brucella abortus

VALGUARNERA E; UGALDE JE

Mendoza

Congreso; XLVIII Reunión Anual SAIB; 2012

Argentine Society for Biochemistry and Molecular Biology Research

Our laboratory has previously identified through an N-terminal CAT-fusion screening, a set of secreted and/or periplasmic proteins in B. abortus. Serendipitously, we observed that a mutant in one of these genes (BAB1_1280) had a growth defective phenotype at 23°C, but grew as the wild type strain at 37°C. For this reason we named this gene cgpA, for Cold Growth Protein A. Sequence and biochemical analysis indicated that CgpAis a small outer membrane associated 9.8 KDa protein present in most alpha-proteobacteria. Our results indicate that the DcgpA growth defective phenotype is due to a lower replication rate rather than a diminished low temperature resistance. This is likely to be the result of a defective metabolic activity at low temperatures. In fact, our results from liquid culture experiments strongly suggest a role for CgpA on the transition from lag phase to log phase at low temperatures. In order to identify other genes that participate in the same cold adaptive pathway, we generated a library of random transposon inserted mutants using the DcgpA mutant strain as the acceptor and selected for growth at 23°C. Using this approach we isolated a set of phenotypic revertants and identified the gene affected in each one. Future characterization of these mutants and the genes affected will provide valuable information about cgpA-dependent low temperature growth in B.abortus.