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Heat shock response in mycoplasmas, genome-limited organisms
C C Dascher1, S K Poddar, J Maniloff
1Department of Microbiology and Immunology, University of Rochester, New York 14642.
Abstract:
We have measured the effect of heat shock on three mycoplasmas (Acholeplasma laidlawii K2 and JA1 and Mycoplasma capricolum Kid) and demonstrated the induction of mycoplasma heat shock proteins under these conditions. Increased synthesis of at least 5 heat shock proteins in A. laidlawii K2, 11 heat shock proteins in A. laidlawii JA1, and 7 heat shock proteins in M. capricolum was observed by electrophoretic analysis of proteins from heat-shocked cells in sodium dodecyl sulfate-polyacrylamide gels. In all three strains, major heat shock proteins (66 to 68 and 26 to 29 kilodaltons [kDa]) were found. The 66- to 68-kDa protein cross-reacted with antibody to Escherichia coli DnaK protein, suggesting that this heat shock protein has been conserved in spite of major reductions in genetic complexity during mycoplasma evolution. A. laidlawii also contained a 60-kDa protein that cross-reacted with eubacterial GroEL protein and a 40-kDa protein that cross-reacted with E. coli RecA protein. Unlike with coliphages, the mycoplasma virus L2 progeny yield was not increased when virus was plated on heat-shocked A. laidlawii host cells. However, UV-irradiated L2 virus could be host cell reactivated by both A. laidlawii SOS repair and heat shock systems.
Insights
Heat shock induces heat shock proteins in mycoplasmas. A conserved heat shock protein (66-68 kDa) in Acholeplasma laidlawii and Mycoplasma capricolum suggests evolutionary conservation despite genetic simplification.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Mycoplasmas are bacteria with reduced genomes.
- Heat shock response is crucial for cellular survival under stress.
- Understanding heat shock proteins (HSPs) in mycoplasmas provides insights into their evolution and stress adaptation.
Purpose of the Study:
- To investigate the effect of heat shock on protein synthesis in three mycoplasma strains.
- To identify and characterize heat shock proteins (HSPs) induced by thermal stress.
- To explore the evolutionary conservation of HSPs in mycoplasmas.
Main Methods:
- Exposure of Acholeplasma laidlawii (K2, JA1) and Mycoplasma capricolum (Kid) to heat shock conditions.
- Electrophoretic analysis (SDS-PAGE) of cellular proteins to detect changes in synthesis.
- Immunological cross-reactivity assays using antibodies against known bacterial proteins (E. coli DnaK, GroEL, RecA).
Main Results:
- Heat shock induced the synthesis of multiple HSPs in all three mycoplasma strains (5-11 proteins).
- Major HSPs (66-68 kDa and 26-29 kDa) were identified across strains.
- The 66-68 kDa HSP showed cross-reactivity with E. coli DnaK, indicating evolutionary conservation.
- A. laidlawii also exhibited cross-reactivity for 60 kDa (GroEL) and 40 kDa (RecA) proteins.
Conclusions:
- Mycoplasmas synthesize specific heat shock proteins in response to thermal stress.
- The presence of DnaK-like protein suggests conservation of essential stress response mechanisms during mycoplasma evolution.
- Mycoplasma virus L2 yield is not increased on heat-shocked cells, but UV-irradiated virus can be reactivated by host cell repair systems.