Differential gene expression in Acidithiobacillus ferrooxidans in response to pH alterations

Author(s)

Rogerio Faria Bergamo

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2007-01-31

Examining board members

Laura Maria Mariscal Ottoboni; Maria Silvia Viccari Gatti; Laurecir Gomes; Edi Lúcia Sartorato; Márcio José da Silva

• Advisor: Laura Maria Mariscal Ottoboni

Abstract

Acidithiobacillus ferrooxidans are non pathogenic, Gram-negative bacteria that obtain energy for growth from the oxidation of inorganic compounds. These bacteria are part of a consortium of microorganisms involved in the bioleaching of metals. Among others, pH alterations can affect bioleaching. The pH is very important in the survival and growth of the bacteria, but very little is known about the molecular mechanisms used by the bacteria to bare pH alterations. This way, in this work respirometric experiments and growth curves were conducted to analyze the behavior of the A. ferrooxidans Brazilian strain LR in situations involving changes in the bacteria ideal pH. In pHs above (2.5 and 3.0) and below (1.5 and 1.2) 1.8 both oxygen consumption and growth were affected. The pHs used in the respirometric experiments and growth curves were selected to grow A. ferrooxidans cells to isolate the RNA that was used in the RAP-PCR experiments with the arbitrary primers OPF01, OPF03, OPF04, OPF08, OPJ04 and OPJ14. The differential expression of the isolated cDNAs was validated by slot blot. The cDNAs were cloned, sequenced and the obtained sequences were compared to the ones present In GenBank. The deduced amino acids sequences of four cDNAS up-regulated in pHs above and below 1.8 presented similarity with the following proteins: hypothetical protein, small heat shock, L-2-haloalkanoic acid dehalogenase and ResB. The deduced amino acids sequences of four cDNAS down-regulated in pHs above and below 1.8 presented similarity with the proteins: fructose/tagatose biphosphate aldolase, DedA, ribosomal protein and ATP-dependent DNA helicase. These results suggest that alterations in the A. ferrooxidans ideal pH change the expression of genes that encode proteins from different functional categories (AU)