Agriculture Reference
In-Depth Information
spore layers have no counterparts in growing cells (Driks 2002a,b; Henriques and
Moran 2007 ).
Spore Morphology
Spore layers, starting from the outside, begin with the exosporium, a balloonlike
structure composed of proteins, some of which are glycoproteins (Driks 2002a;
Henriques and Moran 2007). A large exosporium is not present in spores of all species,
although it is present in spores of a number of species that can cause foodborne disease
(e.g.,
B. anthracis
and
B. cereus
). As far as is known, the exosporium plays little if
any role in spore resistance to chemical agents.
Beneath the exosporium is the spore coat. This structure is composed largely of
protein, with
30 spore - specifi c proteins often in several distinct layers, and a number
of coat proteins are cross-linked to one another (Driks 2002a; Driks 2002b; Henriques
and Moran 2007). The coat plays an important role in imparting spore resistance to
many chemical agents, including chlorine dioxide, sodium hypochlorite, ozone and
other oxidizing agents, because spores in which the majority of coat protein is absent
due either to a defect in coat assembly or chemical extraction are much more sensitive
to these chemicals than are spores with intact coats (Fig. 14.2; see Genest and others
2002; Loshon and others 2001; Paul and others 2006, 2007; Setlow 2006; Young and
Setlow 2003, 2004a,b ).
No specifi c individual protein or proteins have been implicated in spore chemical
resistance, and it has been suggested that the large amount of coat protein (30-50%
≥
Figure 14.2.
Effect of the spore coat on spore resistance to sodium hypochlorite (A)
and chlorine dioxide (B).
B. subtilis
spores either intact or after chemical removal of
≥
50% of coat protein were treated in water with chlorine dioxide or sodium hypochlo-
rite, the reagents were neutralized, and spore viability was determined. Similar results
have been obtained when spores with a genetic defect in coat assembly are tested
(Young and Setlow 2003). The symbols used are
, decoated spores; and
, intact
spores. The data for this fi gure were taken from Young and Setlow (2003).
