Associated Bacteria on Entomopathogens

Almost all of the bacteria that have been isolated from insect are facultative pathogens (Lysenko, 1985). There are still limited evident shown the isolated bacteria from the dead insect body exactly caused the death of the insect or it derived from secondary infection of the dead insect specimen. The bacterial genera belong to the group Enterobacteriaceae and represented by  Escherichia, Alcaligenes, Enterobacter, Achromobacter, Erwinia, Klebsiella, and Serratia  have been isolated from the body of insects (Grimont et al., 1979). Many species of Streptococci, e.g. S. faecalis and S. fecium are the common bacteria found in immature insect, either as normal microflora or as facultative pathogens (Lysenko, 1985).

Due to the limitation of adequate information about the bacterial diversity and also the ecology of host insect itself, the bacterial species associated with insect is considered to be similar in the various habitat. It is possible that the strain of certain bacterial species might be different with the identical species from another habitat. It is also possible that certain bacteria associated with the insect are site specific in another habitat. This type of abundance can be termed as ‘rarely isolated’. The bacterial diversity in entomopathogens related to the type of environments, such as laboratory, cultivated area, and wild nature. The traditional methods in conventional taxonomy seems to be obsolete and failed to describe the unique quality and taxonomy placement of the bacteria associated with entomopathogens (Lysenko, 1985). On the other hand, molecular detection will be very useful to obtain the rarely isolated bacteria and also describe the robust taxonomy of the bacteria associated with entomopathogens. 

The molecular detection approach to identify the associated bacteria on entomopathogens has been reported by several researcher. Babic et al. (2000) on the basis of phenotype characteristic and 16S rRNA analysis showed that Photorhabdus-associated bacteria were closely related to Ochrobactrum anthropi and O. intermedium, Georgieva et al. (2005) during their study about the bacteria associated with Steinernema and Heterorhabditis found Bacillus, Sporosarcina, Planococcus, and Micrococcus other than Xenorhabdus, and also Park et al. (2011) isolated Alcaligenes faecalis, Flavobacterium sp., and Providencia vermicola from the insect-parasitic nematode Rhabditis blumi.

References

Babic, I., Saux, M.F., Giraud, E., and Boemare, N. 2000. Occurrence of natural dixenic associations between the symbiont Photorhabdus luminescens and Bacteria related to Ochrobactrum spp. In tropical entomopathogenic Heterorhabditis spp. (Nematoda, Rhabditida). Microbiology. 146 : 709-718.

Georgieva, Y.H., Groudeva, V.I., and Shishiniova, M.D. 2005. Taxonomic identification of Bacteria, associated with Bulgarian populations of entomopathogenic nematodes from genus Steinernema (Rhabditida, Steinernematidae) II.  Biotechnol. & Biotechnol. Eq. 19 (3).  

Grimont, P.A.D., Grimont, F., and Lysenko, O. 1979. Serratia ficaria sp.nov., a bacterial species associated with Smyrna figs and the fig wasp Blastophage psenes. Curr. Microbiol. 2 : 139-142.  

Lysenko, O. 1985. Non-sporeforming bacteria pathogenic to insects : incidence and mechanisms. Ann. Rev. Microbiol. 39 : 673-95. 

Park, H.W., Kim, Y.O., Ha, J., Youn, S.H., Kim, H.H., Bilgrami, A.L., and Shin, C.S. 2011. Effects of associated bacteria on the pathogenicity and reproduction of the insect-parasitic nematode Rhabditis blumi (Nematoda : Rhabditida). Can. J. Microbiol. 57 : 750-758.