Cloning and purification of the first termicin-like peptide from the cockroach Eupolyphaga sinensis

Termicin is an antimicrobial peptide with six cysteines forming three disulfide bridges that was firstly isolated from the salivary glands and hemocytes of the termite Pseudacanthotermes spiniger. In contrast to many broad-spectrum antimicrobial peptides, termicin is most active against filamentous fungi. Although more than one hundred complementary DNAs (cDNAs) encoding termicin-like peptides have been reported to date, all these termicin-like peptides were obtained from Isoptera insects. Methods The cDNA was cloned by combination of cDNA library construction kit and DNA sequencing. The polypeptide was purified by gel filtration and reversed-phase high performance liquid chromatography (RP-HPLC). Its amino acid sequence was determined by Edman degradation and mass spectrometry. Antimicrobial activity was tested against several bacterial and fungal strains. The minimum inhibitory concentration (MIC) was determined by microdilution tests. Results A novel termicin-like peptide with primary structure ACDFQQCWVTCQRQYSINFISARCNGDSCVCTFRT was purified from extracts of the cockroach Eupolyphaga sinensis (Insecta: Blattodea). The cDNA encoding Es-termicin was cloned by cDNA library screening. This cDNA encoded a 60 amino acid precursor which included a 25 amino acid signal peptide. Amino acid sequence deduced from the cDNA matched well with the result of protein Edman degradation. Susceptibility test indicated that Es-termicin showed strong ability to kill fungi with a MIC of 25 g/mL against Candida albicans ATCC 90028. It only showed limited potency to affect the growth of Gram-positive bacteria with a MIC of 200 g/mL against Enterococcus faecalis ATCC 29212. It was inactive against gram-negative bacteria at the highest concentration tested (400 g/mL). Es-termicin showed high sequence similarity with termicins from many species of termites (Insecta: Isoptera). Conclusions This is the first report of a termicin-like peptide isolated from E. sinensis that belongs to the insect order Blattodea. Our results demonstrate the diversity of termicin-like peptides, as well as antimicrobial peptides in insects.

Genetic variability of Five Periplaneta americana L. (Dyctioptera: Blattidae) populations in southwestern Colombia using the AFLP molecular marker technique

The genetic structure of five Periplaneta americana (L.) populations from three cities (Cali, Popay¨¢n and Buenaventura) located in southwestern Colombia was estimated using the AFLP molecular marker technique. A set of 174 loci were analyzed, 120 of which were polymorphic. Genetic diversity was estimated at different geographic levels for the total population and between cities. Genetic diversity averaged 0.32. The largest gene flow was detected between two population from Cali (F ST = 0.088; Nm = 2.6) and the lowest from the third population in this city (Univalle) and Popay¨¢n and Buenaventura (F ST = 0.13; Nm = 1.6 and F ST = 0.12; Nm = 1.8, respectively). The individuals' low mobility, the population' geographic separation, and possibly genetic drift have resulted in the population of this cockroach species having a significant degree of structuring, both between cities (¦µst = 0.13; P < 0.001) and within them (¦µst = 0.87; P < 0.001). These results suggest a high degree of subdivision within the P. americana population studied.