Agriculture Reference
In-Depth Information
spores (Cortezzo and others 2004). Such sensitivity to high salt content is often
ascribed to damage to membrane functions (Hurst 1977, 1983).
4. Although spore populations killed 90-99% by these agents will germinate, these
germinated “ killed ” spores:
a. Often exhibit little if any metabolic activities
b. Appear to have a severely damaged plasma membrane as determined by staining
with a dye that is excluded from untreated germinated spores
c. Will lyse
d. Even when germinated artifi cially with exogenous lysozyme in a hypertonic
medium, many of these treated spores lyse.
While the available data for killing spores with chlorine dioxide, hypochlorite, or
ozone are most consistent with some sort of damage to the spore inner membrane, the
identity of this damage is not clear, although it is not damage to unsaturated fatty acids
(Cortezzo and others 2004). However, it is clear that spores killed by these agents are
indeed truly dead.
Spore killing by hydrogen peroxide shares some features with spore killing by
chlorine dioxide, hypochlorite, and ozone as noted above, and spore killing by hydro-
gen peroxide may again be in part due to some sort of inner membrane damage.
However, in contrast to the latter three agents that do not kill spores that lack the
majority of their
−
−
spores) by DNA damage, hydrogen peroxide
α
/
β
- type SASP (
α
β
−
spores by DNA damage (Setlow and Setlow 1993). Hydrogen per-
oxide can enter the spore core and damage core components; the other three agents
do not appear to do this at rates suffi cient to cause appreciable spore killing. Once in
the spore core, hydrogen peroxide, and at least some other hydroperoxides effi ciently
inactivate spore core enzymes at rates that are comparable to spore killing (Palop and
others 1996, 1998). Although there is no evidence implicating the inactivation of any
specifi c enzyme by hydrogen peroxide as the cause of spore killing, this mechanism
is consistent with recent work suggesting that the inactivation of one or more core
proteins is the cause of spore killing by wet heat (Coleman and others 2007). There
are also data suggesting that hydrogen peroxide-treated spores can initiate germina-
tion, but they do not proceed into spore outgrowth, consistent with the postulated
mechanism of inactivation of one or more core enzymes (Melly and others 2002).
Although the mechanism of spore killing by hydrogen peroxide has not been specifi -
cally identifi ed in detail, it is clear that spores killed by this agent are indeed dead,
since artifi cial germination of such killed spores does not increase spore recovery
(Melly and others 2002 ).
−
clearly kills
α
β
Novel Chlorine Dioxide Technologies for Eliminating Microbial
Hazards from Fresh Produce and Food-Handling Environments
Aqueous chlorine dioxide provides an effective method for washing minimally pro-
cessed fruits and vegetables and eliminating spoilage microfl ora, vegetative patho-
gens, and bacterial spores of soilborne
Bacillus
and
Clostridium
species to prevent
potential foodborne disease and food spoilage (Rico and others 2007; Gómez-López
and others 2007; Park and others 2008; Mahmoud and Linton 2008; Mahmoud and
