Identification and comparison of macrophage-induced proteins and proteins induced under various stress conditions in Brucella abortus

Abstract

Brucella abortus is a facultative intracellular pathogen of cattle and humans that is capable of survival inside macrophages. In order to understand how B. abortus copes with the conditions during intracellular growth in macrophages, the protein synthesis pattern of the bacteria grown inside bovine macrophages has been compared with that of bacteria grown in the cell culture medium by two-dimensional polyacrylamide gel electrophoresis. Approximately 24 new proteins that are not detected in the bacteria grown in the cell culture medium have been induced during intracellular growth in macrophages. In contrast, approximately 50 proteins that were expressed during growth in cell culture medium were completely repressed during intracellular growth. The level of expression of 19 proteins increases while that of 54 proteins decreases during intracellular growth. To understand these results, the protein synthesis pattern of B. abortus during intracellular growth was compared with those during other stress conditions. Under each stress condition studied, several new proteins were induced that were not present during regular growth conditions. Comparison of the protein synthesis pattern of B. abortus during intracellular growth with those obtained under various stress conditions has indicated that the response to intracellular growth was not just a simple sum of stress conditions studied so far.

A two‐component regulatory system playing a critical role in plant pathogens and endosymbionts is present in Brucella abortus and controls cell invasion and virulence

“…As demonstrated for other two-component regulatory systems, multiple genes should be under the control of BvrR-BvrS. It has been shown recently that, in addition to variations in the level of expression of 73 proteins, repression of 50 in vitro expressed proteins and induction of 24 new proteins occurs during growth of B. abortus within macrophages (Rafie-Kolpin et al, 1996). Interestingly, these authors also showed that, although acid, oxidative, nutritional and heat stresses all induce new proteins (including GroEL, HtrA, SodC and DnaK), the sum of these in vitro induced proteins is not equivalent to those expressed in macrophages.…”

“…In addition, plasmids or lysogenic phages that could transfer virulence genes have not been found despite extensive search (for review see Moreno, 1997). Although B. abortus has been observed to invade cells, to replicate within intracellular compartments (Detilleux et al, 1990a,b) and to modulate protein expression during intracellular growth (Rafie-Kolpin et al, 1996), the mechanisms behind these activities have not been resolved.…”

Cold shock protein A plays an important role in the stress adaptation and virulence ofBrucella melitensis

“…Moreover, the cspA gene was also found to be induced by oxidative stress. Although the functional contributions of CspA to stress tolerance in Brucella are not yet clear, research has shown that Brucella that are grown in macrophages undergo a significant change in protein expression (Lin & Ficht, 1995;Rafie-Kolpin et al, 1996). Because the RNA chaperone Hfq acts as a global regulator in Brucella (Caswell et al, 2012) and CspA is also an RNA chaperone (Jiang et al, 1997) that is linked to the regulation of the expression of multiple genes in E. coli (Bae et al, 1997;Phadtare & Inouye, 2004), an intriguing possibility is that CspA may participate in the regulation of some or all of these proteins involved in stress tolerance.…”

Germination of Bacillus anthracis spores within alveolar macrophages

“…Moreover, this result underlined the existence of inducer(s), belonging to the phagolysosome, that trigger the transcription of the genes encoding virulence factors such as AtxA, PA, LF and EF. This raises the question of the mechanisms by which these genes are expressed after exposure to stress stimuli (Chen et al, 1996;Rafie-Koplin et al, 1996). Toxins may play an essential role as soon as germination occurs and thereby contribute to bacterial survival.…”