Biology Reference
In-Depth Information
TEPHRITIDS AND INTERNAL EXTRACELLULAR BACTERIA
While most of the bacterial associations discussed thus far have been external in nature, it is
important to address the repeated isolation of
spp. internally from the
alimentary-canal organs of several tephritid species, for both adult and larval forms. Despite the
numerous microbial species that
Enterobacter
and
Klebsiella
R. pomonella
consume through their feeding and foraging activ-
ities, only two internal extracellular bacterial species are routinely isolated from the alimentary
canal organs,
Enterobacter
and
Klebsiella
spp. (Lauzon et al., 1998). Lauzon (1991) isolated these
two species from all life stages of
R. pomonella
, and Potter (2001) isolated these two species from
all life stages of
R. completa
. Similarly, these bacterial species have been isolated from the
alimentary canal organs of other tephritids, such as
C. capitata
(Girolami,
1986,
Marchini et al.,
2002),
B. tryoni
(Drew and Lloyd, 1991),
A. ludens
(Rubio and
McFadden,
1966;
Kuzina et al.,
2001),
A. suspensa
(C.R. Lauzon, unpublished data), and
R. completa
(Tsiropoulous, 1976). Lauzon
and Potter (1999) have found that these two bacterial species form an extensive bioÝlm within the
esophageal bulb, crop, and intestines as well as on the apical end of eggs within ovaries (Lauzon
et al., 2002, unpublished data). This specialized, complex assemblage of two bacterial species
further supports the hypothesis (Lauzon et al., 1998 and 2000) that
Enterobacter
and
Klebsiella
spp. jointly participate in the cycling of nitrogen. Keilin (1913) and Vijaysegaran et al. (1997)
suggested that pores, acting as Ýlters in the mouthparts of tephritids, regulated the size and thus
the type of microorganisms that enter the tephritid alimentary canal. Although
Enterobacter
and
Klebsiella
spp. appear to dominate the alimentary canal bioÝlms, other microbial species may
inhabit the bioÝlm and be viable but nonculturable species. Indeed, other bacterial species, such
as
Escherichia coli
, have been isolated from fruit Þies (i.e., Lauzon, 1991). It is likely that these
bacteria are planktonic, transient species that are either digested or pass through the alimentary
canal and exit the Þy rather quickly. Currently, with collaborative efforts from Edouard Jurkevitch
and Boaz Yuval of Hebrew University, we are using molecular techniques to deÝne the bacterial
communities that comprise the bioÝlms.
Few surveys of insect intestines include attempts to isolate anaerobic bacteria. Anaerobic
bacteria are typical inhabitants of the intestinal environments of vertebrate species; however, Potter
(2001) surveyed the intestines of
R. completa
Cresson, the walnut husk Þy, and did not isolate any
anaerobic bacteria from alimentary canal organs of adult and larval
R. completa
. If
Enterobacter
and
Klebsiella
spp. act as the sole important bacterial dual-species system within the fruit Þy gut,
then this simple system can be manipulated more easily and precisely than one that contains
numerous species with numerous interactions (Banks and Bryers, 1991; Siebel and Characklis,
1991). Such research will facilitate a more comprehensive and complete understanding of the
population dynamics of these bacteria within the Þy gut and likely lead to a comprehensive
understanding of the roles these bacteria play with the nutritional and, possibly, the reproductive
physiology of the Þies.
BIOFILMS WITHIN DIGESTIVE AND REPRODUCTIVE
ORGANS AND TEPHRITIDS
In the past, the coordinated assembly of bacteria into a bioÝlm was generally thought to be a
response of microorganisms to unfavorable or suboptimal environmental conditions (Atlas and Bartha,
1987). Today, most researchers contend that bioÝlms are the typical form of microbial communities
and that the bioÝlm structure itself can afford much information about the functions that occur within
the bioÝlm (Costerton et al., 1987, 1995). The microbial species that comprise the bioÝlm also provide
information regarding the metabolic processes or population dynamics that occur within the commu-
nity. In an attempt to learn more about the structure and function of the bioÝlms within tephritids,
my laboratory initiated an examination of the alimentary organs of adult
R. pomonella, R. completa,
A. ludens,
and
C. capitata
using electron and confocal laser scanning microscopy (C.R. Lauzon and
