Antimicrobial activity in the egg wax of the African cattle tick Amblyomma hebraeum (Acari: Ixodidae)

Abstract

Eggs of the tick Amblyomma hebraeum Koch (Acari: Ixodidae) inhibited the growth of Escherichia coli and Serratia marcescens (Gram-negative bacteria) in solid culture, but not the growth of Staphylococcus epidermidis, and only marginally the growth of Bacillus subtilis (Gram-positive bacteria). When egg wax was extracted with chloroform/methanol (2:1), the extract contained antibacterial activity, but the denuded eggs did not. When assayed against bacteria in liquid culture, the aqueous phase inhibited the growth of S. epidermidis. However, the activity against E. coli was lost during extraction. The antimicrobial component of the aqueous phase was heat stable (100 degrees C for 10 min), resistant to proteinase K (15 min at 55 degrees C) and to pronase (30 min at 37 degrees C). The antibacterial activity in the aqueous phase increased the permeability of the cell membrane of susceptible bacterial cells within 30 min. However, lysis of the cells was detected by optical density measurements (OD(600 nm)) only after 1.5 h. The most evident cytological changes observed by transmission electron microscopy were a thickening of the cell wall and the appearance of numerous electron lucent areas within the cytoplasm of treated bacteria. Gené's organ, the egg-waxing organ in ticks, grew enormously during the first 16 days post-engorgement, and gained antimicrobial activity by day 10 (when oviposition began). This suggests that Gené's organ is the major source of the antibacterial substance in the egg wax. The vitellogenic hormone in A. hebraeum, 20-hydroxyecdysone, when injected into recently engorged females, did not stimulate growth of Gené's organ or precocious secretion of antimicrobial activity.

Innate Immunity in Ticks: A review

“…Ixosin is the first antimicrobial peptide lacking cysteine residues isolated from ticks and the purified ixosin displayed antimicrobial activity against Gram-positive and Gram-negative bacteria as well as fungi and low hemolytic activity. Arrieta et al (2006) also reported that the eggs of the African cattle tick Amblyomma hebraeum had antibacterial activity against the Gram-negative bacteria, E. coli and Serratia marcescens. The substance was shown to be heat stable and cause lysis of bacterial cells.…”

Antiviral effect of the egg wax of Amblyomma cajennense (Acari: Ixodidae)

“…Nakajima et al (2003) and Johns et al (1998) have shown the control of bacterial infections in the hard tick Dermacentor variabilis (Acari: Ixodidae) in tick hemolymph by demonstrating the presence of a protein with M(r) 14.5 kDa, that comigrated with human lysozyme, as the protein with potential antimicrobial activity. Recently, Arrieta et al (2006) have shown that egg wax of the African cattle tick Amblyomma hebraeum contained antibacterial activity inhibiting the growth of Escherichia coli and Serratia marcescens (Gramnegative bacteria) in solid culture. They suggest that Gené's organ, (the egg-waxing organ in ticks) is the major source of the antibacterial substance in the egg wax.…”

“…They cover the eggs in a waxy layer produced by an organ known as Gené's Organ to protect them from desiccation and microbial attack. Arrieta et al (2006) studied the wax covering the eggs of the African tick Amblyomma hebreum Koch and successfully demonstrated antimicrobial activity in this wax. The antimicrobial activity of the egg wax from the neotropical tick Amblyomma cajennense (Fabricius) was observed for some microorganism including virus (Lima-Netto et al 2011).…”

Identification of two genes essential for sperm development in the male tick Amblyomma hebraeum Koch (Acari: Ixodidae)

“…However, the fact that the fewer eggs laid by females mated with dsRNA-treated males also shriveled before hatching suggests that there might be some direct effect of gene silencing in the male on the female's reproductive physiology. The female reproductive accessory gland, Gené 's organ, produces a wax that protects the eggs from desiccation and from attack by soil microorganisms (Arrieta et al, 2006). Shriveling of the eggs suggests that the function of Gené 's organ may have been compromised and wax secretion inhibited, although it is certainly not easy to imagine how gene knockdown in the male could directly affect an accessory gland in the female.…”