Biology Reference
In-Depth Information
, Walsh, the apple maggot Þy, occurred
when Allen and Riker (1932) isolated a bacterium reported as
The Ýrst purported symbiont of
Rhagoletis pomonella
Pseudomonas (Phytomonas)
melopthora
(1934) reported that the bacterium
was associated with apple maggot eggs and larvae within rotting host fruit. Continued work by
others (i.e., Baerwald and Boush, 1968; Dean and Chapman, 1973; Rossiter et al., 1983) suggested
that this microorganism had likely been misidentiÝed and perhaps was not a symbiote of
in soft rot of apple tissue. Subsequently, Allen
et al.
R.
pomonella
. It is evident that the problems associated with this research and that of the olive Þy lay
with the microbiological accuracy of the research.
Howard et al. (1985) suggested that while bacteria were associated with the apple maggot Þy,
no bacterium appeared to be in an obligate symbiotic relationship with the apple maggot Þy. This
contention was questioned when Lauzon (1991) isolated a bacterium,
Enterobacter agglomerans,
from oviposition sites in apple and eggs of
The bacterium was often isolated in pure
culture prior to invasion by other microorganisms into the oviposition site and larval development.
Although an obligatory relationship has yet to be determined between
R. pomonella.
and any
tephritid, evidence is presented below that suggests that this bacterium and one other bacterial
species,
E. agglomerans
, are involved in the life history of several tephritid species.
Since the time of HowardÔs work, certain bacterial species have been routinely isolated from
Klebsiella pneumoniae
R. pomonella,
and other pest tephritids, notably enteric and environmental species such as
Enter-
obacter
spp. The commonality of isolation of these species from both temperate
and tropical tephritids suggests that though bacterial associations may not be obligatory, these two
bacterial genera likely play an important role in the life history and, importantly, in the ecology of
these pests (Drew and Lloyd, 1991).
The common but not exclusive isolation of certain members of the family Enterobacteriaceae,
notably
and
Klebsiella
spp., internally from pest tephritids and oviposition sites (i.e.,
Petri, 1909; Allen et al., 1934; Rubio and McFadden, 1966; Hagen, 1966; Boush and Matsumura,
1967; Dean and Chapman, 1973; Rossiter et al., 1983; Howard et al., 1985; Girolami, 1986; Drew
and Lloyd, 1987; Lauzon, 1991; Kuzina et al., 2001; Potter, 2001)
Enterobacter
and
Klebsiella
has stimulated interest for some
researchers to continue deÝning the possible relationships that might exist between tephritids and
certain bacterial species. The relationships may range from bacteria serving as food and contributors
of host-plant cues to being detoxiÝers of synthetic and natural pesticides or plant defensive com-
pounds.
It is likely that bacteria provide diverse metabolic and physiological capabilities that impact
tephritids in equally diverse ways. It is also possible that no one role may dominate under all
environmental conditions. For example, a bacterium may give off odors indicative of quality food
when it is actively growing within fecal material; then, the bacterium may subsequently serve as
a digester of nitrogen when it resides in an insect gut. Also, one catabolic activity afforded by a
bacterium could result in several beneÝts to a tephritid. For example, degrading host tissue could
afford both food and easier movement for a larva throughout a host fruit. Hence, it may be more
prudent to view microbialÏtephritid associations in holistic, expanded ways than to rely on reduc-
tionist approaches from some previous research.
In the early 1970s, Dean and Chapman (1973) found large numbers of bacteria within the crop
of
. The possibility that bacteria might serve as a source of food and not play any
obligatory symbiotic role was subsequently evaluated. Drew et al. (1983) found that bacteria served
as an adequate breeding diet for
R. pomonella
and as a continuation of this work Courtice
and Drew (1984) initiated studies that attempted to explain the relationship between bacteria and
adult fruit Þies from a nutritional standpoint. They suggested that leaf-surface bacteria were
important sources of adult food, and once Þies ingested bacteria, the bacteria were lysed within
the acidic, pH 3 gut and the cellular contents served as nutrients. In addition, Drew and Lloyd
(1987) reported that bacteria colonizing
Bactrocera tryoni,
were utilized by females to produce eggs.
Furthermore, in the same paper they linked members of the genera
B. tryoni
Enterobacter
and
Klebsiella
spp.
with
B. tryoni
and the pestÔs host plant. They found that prior to oviposition into host fruit,
B. tryoni
would regurgitate these bacteria on the fruit surface, reverse their position, and oviposit
