Induced Hatching of Quiescent Aedes aegypti (Diptera: Culicidae) Eggs by Labile Glutathione-Stabilizable Compounds From Yeast Extract.

Aedes aegypti (Linnaeus, 1762) is the insect vector that transmits several deadly human diseases. Although the egg stage is an important phase of its life cycle, the biology of mosquito egg remains poorly understood. Here, we report our investigations on the chemical factors that induced hatching of Ae. aegypti eggs. Commercial yeast extracts were able to increase egg hatching rate in a dose-dependent manner, with a hatching rate that ranged from approximately 10% with 1 g/liter to 80% with 20 g/liter of yeast extract. Notably, the addition of glutathione, a reducing agent that showed no significant effect on egg hatching by itself, enhanced and stabilized the activity of yeast extract for at least 70 h. Because dissolved oxygen in different treatments was maintained at high levels in a narrow range (92-95%), we proposed that yeast extract contains hatching inducing compound (HIC) which is able to trigger egg hatching independent of dissolved oxygen level. The HIC in yeast extract could prove to be a potential starting point to design an effective tool to forcefully induce mosquito eggs to hatch under unfavorable conditions, functioning as a novel method for vector control.

Sphingomonas palmae sp. nov. and Sphingomonas gellani sp. nov., endophytically associated phyllosphere bacteria isolated from economically important crop plants.

In this study, two endophytic bacterial strains designated JS21-1T and S6-262T isolated from leaves of Elaeis guineensis and stem tissues of Jatropha curcas respectively, were subjected for polyphasic taxonomic approach. On R2A medium, colonies of strains JS21-1T and S6-262T are orange and yellow, respectively. Phylogenetic analyses using 16S rRNA gene sequencing and whole-genome sequences placed the strains in distinct clades but within the genus Sphingomonas. The DNA G + C content of JS21-1T and S6-262T were 67.31 and 66.95%, respectively. Furthermore, the average nucleotide identity and digital DNA-DNA hybridization values of strains JS21-1T and S6-262T with phylogenetically related Sphingomonas species were lower than 95% and 70% respectively. The chemotaxonomic studies indicated that the major cellular fatty acids of the strain JS21-1T were summed feature 8 (C18:1 ω7c and/or C18:1 ω6c), C16:0, and C14:0 2OH; strain S6-262T possessed summed feature 3 (C16:1 ω7c and/or iso-C15:0 2-OH) and summed feature 8 (C18:1 ω6c and/or C18:1 ω7c). The major quinone was Q10, and the unique polyamine observed was homospermidine. The polar lipid profile comprised of mixture of sphingoglycolipid, phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and certain uncharacterised phospholipids and lipids. Based on this polyphasic evidence, strains JS21-1T and S6-262T represent two novel species of the genus Sphingomonas, for which the names Sphingomonas palmae sp. nov. and Sphingomonas gellani sp. nov. are proposed, respectively. The type strain of Sphingomonas palmae sp. nov. is JS21-1T (= DSM 27348T = KACC 17591T) and the type strain of Sphingomonas gellani sp. nov. is S6-262T (= DSM 27346T =  KACC 17594T).

Chitinasiproducens palmae gen. nov., sp. nov., a new member of the family Burkholderiaceae isolated from leaf tissues of oil palm (Elaeis guineensis Jacq.).

A Gram-stain-negative, aerobic, rod-shaped, leaf-associated bacterium, designated JS23T, was isolated from surface-sterilized leaf tissue of an oil palm grown in Singapore and was investigated by polyphasic taxonomy. Phylogenetic analyses based on 16S rRNA gene sequences and 180 conserved genes in the genome of several members of Burkholderiaceae revealed that strain JS23T formed a distinct evolutionary lineage independent of other taxa within the family Burkholderiaceae. The predominant ubiquinone was Q-8. The primary polar lipids were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, and an unidentified aminophospholipid. The major fatty acids were C16 : 0, summed feature 3 (C16 : 1 ω7c /C16 : 1 ω6c) and summed feature 8 (C18 : 1 ω7c /C18 : 1 ω6c). The size of the genome is 5.36 Mbp with a DNA G+C content of 66.2 mol%. Genomic relatedness measurements such as average nucleotide identity, genome-to-genome distance and digital DNA-DNA hybridization clearly distinguished strain JS23T from the closely related genera Burkholderia, Caballeronia, Mycetohabitans, Mycoavidus, Pandoraea, Paraburkholderia, Robbsia and Trinickia. Furthermore, average amino acid identity values and the percentages of conserved proteins, 56.0-68.4 and 28.2-45.5, respectively, were well below threshold values for genus delineation and supported the assignment of JS23T to a novel genus. On the basis of the phylogenetic, biochemical, chemotaxonomic and phylogenomic evidence, strain JS23T is proposed to represent a novel species of a new genus within the family Burkholderiaceae, for which the name Chitinasiproducens palmae gen. nov., sp. nov., is proposed with the type strain of JS23T (= DSM 27307T=KACC 17592T).

Phytobacter palmae sp. nov., a novel endophytic, N2 fixing, plant growth promoting Gammaproteobacterium isolated from oil palm (Elaeis guineensis Jacq.).

A novel strain S29T with high nitrogen fixing ability was isolated from surface-sterilized leaf tissues of oil palm (Elaeis guineensis) growing in Science Park II, Singapore. On the basis of 16S rRNA gene analysis and multilocus sequence typing with the rpoB, gyrB, infB and atpD genes, strain S29T was a member of the genus Phytobacter, with Phytobacter ursingii ATCC 27989T and Phytobacter diazotrophicus LS 8T as its closest relatives. Unique biochemical features that differentiated strain S29T from its closest relatives were the ability to utilize melibiose, α-cyclodextrin, glycogen, adonital, d-arabitol, m-inositol and xylitol. The major fatty acids were C14 : 0, C16 : 0, C17 : 0, C16 : 1 ω5c and summed feature 2 containing C16 : 1 ω7c and/or C16 : 1 ω6c. The polar fatty acid profile consisted of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, an unidentified aminophospholipid and aminolipids. The draft genome of strain S29T comprised 5, 284, 330 bp with a G + C content of 52.6 %. The average nucleotide identity and digital DNA-DNA hybridization values between strain S29T and the phylogenetically related Enterobacterales species were lower than 95 % and 70 %, respectively. Thus, the polyphasic evidences generated through the phenotypic, chemotaxonomic and genomic methods confirmed that strain S29T represents a novel species of the genus Phytobacter, for which we propose the name Phytobacter palmae sp. nov. with the type strain of S29T (=DSM 27342T=KACC 17598T).

Sphingomonas jatrophae sp. nov. and Sphingomonas carotinifaciens sp. nov., two yellow-pigmented endophytes isolated from stem tissues of Jatropha curcas L.

Two yellow-pigmented isolates, S5-249T and L9-754T, originating from surface-sterilized plant tissues of Jatropha curcas L. (Jatropha) cultivars were characterized using a polyphasic taxonomic approach. Strains S5-249T and L9-754T had 16S rRNA genes sharing 94.2 % sequence similarity with each other and 91.6-97.2 % sequence similarity with those of other species in the genus Sphingomonas, suggesting that they represent two potentially novel species. The 16S rRNA gene sequences of strains S5-249T and L9-754T shared the highest similarity to that of Sphingomonas sanguinis NBRC 13937T (96.1 and 97.2 %, respectively). The genomic DNA G+C contents of strains S5-249T and L9-754T were 66.9 and 68.5 mol%, respectively. The respiratory quinone was determined to be Q-10, and the major polyamine was homospermidine. Strains S5-249T and L9-754T contained summed feature 7 (comprising C18 : 1ω7c, C18 : 1ω9t and/or C18 : 1ω12t), C16 : 1, C14 : 0 2-OH and summed feature 4 (C16 : 1ω7t, iso-C15 : 0 2-OH and C16 : 1ω7c) as the major cellular fatty acids. The predominant polar lipids were phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine and sphingoglycolipid. The average nucleotide identity (ANI) values between S. sanguinis NBRC 13937T and the two type strains (S5-249T and L9-754T) were 72.31 and 77.73 %, respectively. Digital DNA-DNA hybridization (dDDH) studies between the novel strains (S5-249T and L9-754T) and other species of the genus Sphingomonas were well below the thresholds used to discriminate between bacterial species. The results of dDDH and physiological tests allowed genotypic and phenotypic differentiation of the strains from each other as well as from the species of the genus Sphingomonas with validly published names. These data strongly support the classification of the strains as representatives of novel species, for which we propose the names Sphingomonas jatrophae sp. nov. (type strain S5-249T=DSM 27345T=KACC 17593T) and Sphingomonas carotinifaciens sp. nov. (type strain L9-754T=DSM 27347T=KACC 17595T).

Jatrophihabitans endophyticus gen. nov., sp. nov., an endophytic actinobacterium isolated from a surface-sterilized stem of Jatropha curcas L.

A short rod-shaped Gram-stain-positive actinobacterium was isolated as an endophyte from the tissues of Jatropha curcas cv. KB27 and was investigated by means of a polyphasic taxonomic approach. An analysis of its 16S rRNA gene sequence indicated that strain S9-650(T) forms an individual line of descent and is related to certain members of the suborder Frankineae, order Actinomycetales (<95 % sequence similarity). Distance-matrix and neighbour-joining analyses set the branching point of the novel isolate between two clades, one being represented by members of the genera Frankia (family Frankiaceae) and Acidothermus (family Acidothermaceae) and the other by members of the genera Geodermatophilus, Blastococcus and Modestobacter (family Geodermatophilaceae). The organism had meso-diaminopimelic acid as the diagnostic diamino acid in the cell-wall peptidoglycan. The acyl type was found to be N-glycolylated. The major menaquinone was MK-9(H4) and the fatty acid profile was characterized by the predominance of iso-C16 : 0, C18 : 1ω9c, anteiso-C17 : 0 and C17 : 1ω8c. The polar lipids comprised diphosphatidylglycerol, an unidentified glycolipid, phospholipids and aminolipids. The G+C content of the genomic DNA was 71.2 mol%. The distinct phylogenetic position and the phenotypic markers that clearly separate the novel organism from all other members of the suborder Frankineae indicate that strain S9-650(T) represents a novel species in a new genus, for which the name Jatrophihabitans endophyticus gen. nov., sp. nov. is proposed. The type strain of the type species is S9-650(T) ( = DSM 45627(T) = KACC 16232(T)).