Antimicrobial Activity of Compounds Isolated from the Nest Material of Crematogaster rogenhoferi (Mayr) (Hymenoptera: Formicidae)

Ants as social insects live in groups, which increases the risk of contagious diseases. In response to the threat of pathogens, ants have evolved a variety of defense mechanisms, including incorporating antimicrobial chemicals into nest material for nest hygiene. <i>Crematogaster rogenhoferi</i> is an arboreal ant, building its nest using plant tissues. It is still unclear how <i>C. rogenhoferi</i> is protected against pathogens in its nest. Two main chemicals, 2,2'-methylenebis[6-(1,1-dimethylethyl)-4-methyl-phenol] (MP) and lup-20(29)-en-3-one (LP), isolated from nest materials of <i>C. rogenhoferi</i> were used to investigate ants' anti-pathogenic activity against the entomopathogenic fungus <i>Beauveria bassiana</i> and the entomopathogenic bacteria <i>Serratia marcescens</i>. The results showed that MP and LP can inhibit the growth of <i>B. bassiana</i> through direct contact and fumigation. However, neither MP nor LP had any negative effect on <i>S. marcescens</i> growth. Subsequent analysis showed that MP was found in both the abdomen part and the head part of <i>C. rogenhoferi</i> workers, and LP was not detected in <i>C. rogenhoferi</i> workers. Since LP is a common plant secondary metabolite, it is implied that LP may originate from the plant tissue of <i>C. rogenhoferi</i> nest materials. Our results showed that <i>C. rogenhoferi</i> capitalizes on its own antimicrobial chemicals and probably the chemical defenses which have evolved in plants to protect itself against pathogens.