Bacteria as a source of oviposition attractant for Aedes aegypti mosquitoes.

Since a safe and effective mass vaccination program against dengue fever is not presently available, a good way to prevent and control dengue outbreaks depends mainly on controlling the mosquito vectors. Aedes aegypti mosquito populations can be monitored and reduced by using ovitraps baited with organic infusions. A series of laboratory experiments were conducted which demonstrated that the bacteria in bamboo leaf infusion produce volatile attractants and contact chemical stimulants attractive to the female mosquitoes. The results showed that the female mosquitoes laid most of their eggs (59.9 ± 8.1 vs 2.9 ± 2.8 eggs, P<0.001) in bamboo leaf infusions when compared to distilled water. When the fresh infusion was filtered with a 0.45 µm filter membrane, the female mosquitoes laid significantly more eggs (64.1 ± 6.6 vs 4.9 ± 2.6 eggs, P<0.001) in unfiltered infusion. However when a 0.8 µm filter membrane was used, the female laid significantly more eggs (62.0 ± 4.3 vs 10.1 ± 7.8 eggs, P<0.001) in filtrate compared to a solution containing the residue. We also found that a mixture of bacteria isolated from bamboo leaf infusion serve as potent oviposition stimulants for gravid Aedes mosquitoes. Aedes aegypti laid significantly more eggs (63.3 ± 6.5 vs 3.1 ± 2.4 eggs, P<0.001) in bacteria suspension compared to sterile R2A medium. Our results suggest microbial activity has a role in the production of odorants that mediate the oviposition response of gravid mosquitoes.

Leucobacter margaritiformis sp. nov., isolated from bamboo extract.

A Gram-positive aerobic rod-shaped non-motile bacterium designated A23(T) was isolated from bamboo extract that had been used to remove odor and was characterized to determine its taxonomic position. 16S rRNA gene sequence analysis revealed that strain A23(T) belongs to the phylum Actinobacteria. The highest degree of sequence similarities was determined to be with Leucobacter salsicius M1-8(T) (96.7%), Leucobacter exalbidus K-540B(T) (96.4%), Leucobacter chromiireducens subsp. chromiireducens L-1(T) (96.4%), Leucobacter komagatae IFO 15245(T) (96.4%) and Leucobacter aerolatus Sj10(T) (96.4%). Chemotaxonomic data revealed that strain A23(T) possesses menaquinone MK11, and its cell wall peptidoglycan contained 2,4-diaminobutyric acid, alanine, glycine, glutamic acid and γ-aminobutyric acid. The polar lipid profile of strain A23(T) contained diphosphatidylglycerol, phosphatidylglycerol and an unknown glycolipid. The predominant fatty acids were iso-C(16:0) (31.5%), anteiso-C(15:0) (43.2%) and anteiso-C(17:0) (13.9%), all of which corroborated the assignment of the strain to the genus Leucobacter. Based on these data, A23(T) (=KEMC 551-022(T) = JCM 17538(T)) should be classified as the type strain for a novel Leucobacter species, for which the name Leucobacter margaritiformis sp. nov. is proposed.