Areas of Interest
Spores of bacteria of Bacillus species are extraordinarily
resistant to all manner of harsh treatments, and largely because
of this resistance, spores of some Bacillus species are major
agents of food spoilage and food-borne and other diseases (eg-Bacillus
anthracis). The conversion of a dormant Bacillus spore into a
vegetative bacterium by the process of spore germination is also
a relatively simple differentiating system that is readily
amenable to both biochemical and genetic analysis. While much
has been learned in recent years on the mechanisms of spore
resistance and germination, there is still much that is unknown.
Dr. Setlow's laboratory has ongoing multidisciplinary research
projects attempting to determine: 1) the mechanisms involved in
the extraordinary resistance of spores to heat and oxidizing
agents; 2) the mechanism(s) of spore germination and its
heterogeneity; and 3) the structure and organization of the
inner membrane of spores. Methods used in these projects
include: 1) molecular biology to make directed mutants in key
spore genes; 2) confocal fluorescence spectroscopy to localize
and co-localize proteins in spores; 3) determination of
structures of key spore germination and resistance proteins by
X-ray crystallography; 4) classical genetics to identify new
genes important in aspects of spore germination and resistance;
5) identify new factors important in spore resistance; 6)
determine the mechanism(s) whereby moist heat, the most commonly
used method to kill spores, actually works to kill spores; and
7) determine factors responsible for the extreme heterogeneity
in spore germination such that while most spores in populations
germinate within 30 min of addition of a germinant, a small
percentage of spores may not germinate for hours or even days.
Lab Rotation Projects
Lab Rotation Projects can involve the use of many, many
different techniques and include:
1) Overexpression, purification and crystallization of
several proteins involved in spore germination.
2) Analysis of the mechanism of the “commitment” of
spores to germinate, and what factors influence this commitment.
3) Analysis of the role of divalent cations, especially
Mn2+ ions, in protecting spores against a variety of oxidizing
agents;
4) Isolate and characterize mutant Bacillus subtilis
strains that are defective in germination with multiple nutrient
germinants, as such mutants might allow identification of a
putative “integrator” protein that sums up signals from many
different germinants to “direct” a rate of spore germination
appropriate for the germination condition;
5) Isolate a mutant defective in the germination with
cationic surfactants that appear to work by interactinf directly
with the spore’s plasma membrane in some fashion.
6) Construction of a functional fusion to Green
Fluorescent Protein (GFP) to a germination protein and
localization of this GFP fusion in spores, as well as
colocalization with other germination proteins;
7) Use electron microscopy to probe for the existence of
a close packed array of spore germination proteins in the
spore’s plasma membrane.
Selected Publications
Qiu, X, and P. Setlow. (2010) Structural and genetic analysis
of the X-ray scattering by spores of Bacillus subtilis. J.
Bacteriol. In press.
Setlow, P. (2010) Resistance of bacterial spores. In G. Storz
and R. Hengge (ed.), Bacterial Stress Response, 2nd edition.
American Society for Microbiology, Washington, DC. In press.
Wei, J., P. Setlow and D.G. Hoover. (2009) Effects of
moderately high pressure plus heat on the germination and
inactivation of Bacillus cereus spores lacking proteins involved
in germination. Lett. Appl. Microbiol. In press.
Sunde, E.P., P. Setlow, L. Hederstedt and B. Halle. (2009)
The physical state of water in bacterial spores. Proc. Natl.
Acad. Sci. USA in press.
Zhang, P., P. Setlow and Y.-q. Li (2009) Characterization of
single heat-activated Bacillus spores using laser tweezers Raman
spectroscopy. Optics Express 17:16480-16491.
Coleman, W.H., and P. Setlow. (2009) Analysis of damage due
to moist heat treatment of spores of Bacillus subtilis. J. Appl.
Microbiol. 106:1600-1607.
Griffiths, K., and P. Setlow. (2009) Effects of modification
of membrane lipid composition on Bacillus subtilis sporulation
and spore properties. J. Appl. Microbiol. 106:2064-2078.
Setlow, B., L. Peng, C.A. Loshon, Y.Q. Li, G. Christie and P.
Setlow. (2009) Characterization of the germination of Bacillus
megaterium spores lacking enzymes that degrade the spore cortex.
J. Appl. Microbiol. 107:318-328.
Setlow, P. (2008) Bacterial endospores: mechanisms that
contribute to their longevity and resistance. In Biological
Indicators for Sterilization Processes (M. Gómez and J.
Molenhauer, ed.), pp. 25-54. DHI Publishing, River Grove, IL.
Ghosh, S., and P. Setlow. (2009) Isolation and
characterization of superdormant spores of Bacillus species. J.
Bacteriol. 191:1787-1797.
Paredes-Sabja, D., P. Setlow and M. R. Sarker. (2009) SleC is
essential for cortex peptidoglycan hydrolysis during germination
of spores of the pathogenic bacterium Clostridium perfringens.
J. Bacteriol. 191:2711-2720.
Paredes-Sabja, D., P. Setlow and M. R. Sarker. (2009) Role of
GerKB in germination and outgrowth of Clostridium perfringens
spores. Appl. Environ. Microbiol. 75:3813-3817.
Indest, K.J., W.G. Buchholz, J.R. Faeder and P. Setlow (2009)
Workshop report: Modeling the molecular mechanism of bacterial
spore germination and elucidating reasons for germination
heterogeneity. J. Food Sci. 74:R73-R78.
Peng, L., D. Chen, P. Setlow and Y.-Q. Li. (2009) Elastic and
inelastic light scattering from single bacterial spores in an
optical trap allows monitoring of spore germination dynamics.
Anal. Chem. 81:4035-4042.
Paredes-Sabja, D., P. Setlow and M.R. Sarker (2009) GerO, a
putative Na+/H+-K+ antiporter, is essential for normal
germination of spores of the pathogenic bacterium Clostridium
perfringens. J. Bacteriol. 191:3822-3831.
Setlow, P., C.J. Doona, F.E. Feeherry, K. Kustin, D. Sisson
and S. Chandra. (2009) Enhanced safety and extended shelf life
of fresh produce for the military. In Microbial Safety of Fresh
Produce: Challenges, Perspectives and Strategies (X. Fan, C.J.
Doona, F.E. Feeherry and R.B. Gravani, ed.), pp. 263-288.
Wiley-Blackwell, Ames, IA.
Moeller, R., P. Setlow, G. Reitz and W.L. Nicholson. (2009)
Roles of small, acid-soluble spore proteins and core water
content in survival of Bacillus subtilis spores exposed to
environmental solar UV radiation. Appl. Environ. Microbiol.
75:5202-5208.
Ghosh, S., and P. Setlow. (2009) The preparation, germination
properties and stability of superdormant spores of Bacillus
cereus. J. Appl. Microbiol. In press.
Paredes-Sabja, D., P. Setlow and M. Sarker. (2009) The
protease CspB is essential for initiation of cortex hydrolysis
and DPA release during germination of spores of Clostridium
perfringens. Microbiology. 155:3464-3472.
Ghosh, S., P. Zhang, Y.-q. Li and P. Setlow. (2009)
Superdormant spores of Bacillus species have elevated wet heat
resistance and temperature requirements for heat activation. J.
Bacteriol. 191:5584-5591.
Setlow, P. (2008) Dormant spores receive an unexpected wakeup
call. Cell 135:410-412. |
