Transcriptional activity around bacterial cell death reveals molecular biomarkers for cell viability.
BACKGROUND
In bacteriology, the ability to grow in selective media and to form colonies on nutrient agar plates is routinely used as a retrospective criterion for the detection of living bacteria. However, the utilization of indicators for bacterial viability-such as the presence of specific transcripts or membrane integrity-would overcome bias introduced by cultivation and reduces the time span of analysis from initiation to read out. Therefore, we investigated the correlation between transcriptional activity, membrane integrity and cultivation-based viability in the Gram-positive model bacterium Bacillus subtilis.


RESULTS
We present microbiological, cytological and molecular analyses of the physiological response to lethal heat stress under accurately defined conditions through systematic sampling of bacteria from a single culture exposed to gradually increasing temperatures. We identified a coherent transcriptional program including known heat shock responses as well as the rapid expression of a small number of sporulation and competence genes, the latter only known to be active in the stationary growth phase.


CONCLUSIONS
The observed coordinated gene expression continued even after cell death, in other words after all bacteria permanently lost their ability to reproduce. Transcription of a very limited number of genes correlated with cell viability under the applied killing regime. The transcripts of the expressed genes in living bacteria -- but silent in dead bacteria-include those of essential genes encoding chaperones of the protein folding machinery and can serve as molecular biomarkers for bacterial cell viability.
Kort
Remco
R
TNO Quality of Life, Business Unit Food and Biotechnology Innovations, Microbial Genomics Group, Utrechtseweg 48, Zeist, The Netherlands. remco.kort@tno.nl
Keijser
Bart J
BJ
Caspers
Martien P M
MP
Schuren
Frank H
FH
Montijn
Roy
R
D001412:Bacillus subtilis / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D015415:Biomarkers; D015169:Colony Count, Microbial; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D018869:Heat-Shock Response / Q000235:genetics; D006358:Hot Temperature; D050296:Microbial Viability; D005810:Multigene Family; D020411:Oligonucleotide Array Sequence Analysis; D020871:RNA Stability; D012329:RNA, Bacterial / Q000235:genetics; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D015415:Biomarkers; D012329:RNA, Bacterial