Publications

4683

AbstractBACKGROUND: In the present investigation, the effect of Candidatus Liberibacter asiaticus (Las), a bacterium considered to be responsible for causing huanglongbing (HLB) disease in citrus, on the physiology of its vector, the Asian citrus psyllid (ACP) Diaphorina citri Kuwayama, was determined. Specifically, the effects of Las infection on the susceptibility of ACP to selected insecticides were determined. Furthermore, total protein content and general esterase activity were quantified in Las‐infected and uninfected ACP to gain insight into the possible mechanism(s) responsible for altered susceptibility to insecticides owing to Las infection.RESULTS: LC50 values were significantly lower in Las‐infected than in uninfected ACP adults for chlorpyrifos and spinetoram. Furthermore, there was a general trend towards lower LC50 values for three other insecticides for Las‐infected ACP; however, the differences were not statistically significant. Total protein content (µg mL−1) was significantly lower in Las‐infected (23.5 ± 1.3 in head + thorax; 27.7 ± 1.9 in abdomen) than in uninfected (29.7 ± 2.1 in head + thorax; 35.0 ± 2.3 in abdomen) ACP. Likewise, general esterase enzyme activity (nmol min−1 mg−1 protein) was significantly lower in Las‐infected (111.6 ± 4.5 in head + thorax; 109.5 ± 3.7 in abdomen) than in uninfected (135.9 ± 7.5 in head + thorax; 206.1 ± 23.7 in abdomen) ACP.CONCLUSION: Susceptibility of ACP to selected insecticides from five major chemistries was greater in Las‐infected than in uninfected ACP. The lower total protein content and reduced general esterase activity in Las‐infected than in uninfected ACP may partly explain the observed higher insecticide susceptibility of Las‐infected ACP. Copyright © 2010 Society of Chemical Industry

A novel aerobic, heterotrophic bacterium, designated BiosLi39T, was isolated from the South East Pacific Ocean. Cells were Gram-negative gliding rods forming yellow colonies on marine agar. The isolate was oxidase-, catalase- and alkaline phosphatase-positive andβ-galactosidase-negative. Strain BiosLi39Tgrew at 20-37 °C (optimum 30 °C), at pH 7.0–9.0 (optimum pH 8.0) and with 20–60 g NaCl l−1(optimum 30–50 g NaCl l−1). The fatty acids (>1 %) comprised iso-C14 : 0, iso-C15 : 1G, iso-C15 : 0, anteiso-C15 : 0, C15 : 1G, C15 : 0, iso-C15 : 02-OH, iso-C16 : 1G, iso-C16 : 0, iso-C16 : 03-OH, iso-C16 : 02-OH, iso-C17 : 03-OH, C17 : 02-OH and three unidentified components with equivalent chain lengths of 17.87, 18.10 and 18.71. A significant proportion of the hydroxylated fatty acids are amide-linked. The lipid pattern indicated the presence of phosphatidylethanolamine, two unidentified aminolipids and three unidentified polar lipids. The strain contained menaquinone 7 as the sole respiratory lipoquinone and did not produce flexirubin-type pigments. The G+C content of the genomic DNA was 37.2 mol%. Comparative 16S rRNA gene sequence analysis indicated that strain BiosLi39Twas distantly related to all of the representatives of the phylumBacteroidetes. Its closest relative wasMarinoscillum furvescensIFO 15994T, with which it shared 92.5 % 16S rRNA gene sequence similarity. On the basis of genotypic, phenotypic and chemotaxonomic characteristics, we propose a novel genus and species,Ekhidnagen. nov., sp. nov., with type strain BiosLi39T(=DSM 19307T=CIP 109600T=OOB 398T).