Relationships Among Eucheuma-Denticulatum, Eucheuma-Isiforme and Kappaphycus-Alvarezii (Gigartinales, Rhodophyta) Based On Nuclear Ssu-Ribosomal-Rna Gene-Sequences

The nuclear genes encoding small-subunit ribosomal RNAs (ssu-rDNAs) of the carrageenophytes Eucheuma denticulatum, E. isiforme and Kappaphycus alvarezii were amplified by the polymerase chain reaction, cloned and sequenced. The sequences range from 1767 (K. alvarezii) to 1781 (E. isiforme) nucleotides in length, and have guanine+cytosine contents between 51.2% (E. isiforme) and 51.5% (E. denticulatum). Pairwise sequence identities among these sequences ranged from 97.6% to 98.5%, levels comparable to some intergeneric identities within Gracilariales. In phylogenetic analyses, the two Eucheuma ssu-rDNAs group stably together vis-a-vis the ssu-rDNA of K. alvavezii, and these three ssu-rDNAs form a monophyletic group within a larger grouping of other carrageenophytes. The results demonstrate quantitatively that analysis of nuclear-encoded ssu-rDNA sequences is likely to be useful. in resolving taxonomic, phylogenetic and biogeographic questions among tribe Eucheumatoideae Doty

The susceptibility of five African <it>Anopheles</it> species to <it>Anabaena</it> PCC 7120 expressing <it>Bacillus thuringiensis</it> subsp. <it>israelensis</it> mosquitocidal <it>cry</it> genes

<p>Abstract</p> <p>Background</p> <p>Malaria, one of the leading causes of death in Africa, is transmitted by the bite of an infected female <it>Anopheles</it> mosquito. Problems associated with the development of resistance to chemical insecticides and concerns about the non-target effects and persistence of chemical insecticides have prompted the development of environmentally friendly mosquito control agents. The aim of this study was to evaluate the larvicidal activity of a genetically engineered cyanobacterium, <it>Anabaena</it> PCC 7120#11, against five African <it>Anopheles</it> species in laboratory bioassays.</p> <p>Findings</p> <p>There were significant differences in the susceptibility of the anopheline species to PCC 7120#11. The ranking of the larvicidal activity of PCC 7120#11 against species in the <it>An. gambiae</it> complex was: <it>An. merus</it> <<it>An. arabiensis</it> <<it>An. gambiae</it> <<it>An. quadriannulatus</it>, where < indicates a statistically lower LC₅₀. The LC₅₀ of PCC 7120#11 against the important malaria vectors <it>An. gambiae</it> and <it>An. arabiensis</it> was 12.3 × 10⁵ cells/ml and 8.10 × 10⁵ cells/ml, respectively. PCC 7120#11 was not effective against <it>An. funestus</it>, with less than 50% mortality obtained at concentrations as high as 3.20 × 10⁷ cells/ml.</p> <p>Conclusions</p> <p>PCC 7120#11 exhibited good larvicidal activity against larvae of the <it>An. gambiae</it> complex, but relatively weak larvicidal activity against <it>An. funestus</it>. The study has highlighted the importance of evaluating a novel mosquitocidal agent against a range of malaria vectors so as to obtain a clear understanding of the agent’s spectrum of activity and potential as a vector control agent.</p