New Metabolites of Streptomyces alboniger

A mutant unable to grow under acidic conditions was isolated from the acidophilic heterotrophic bacterium Acidiphilium facilis 24R. The growth of the mutant could be fully restored by the addition of spermidine or lysine at the concentration of 100 μm. The HPLC analysis of polyamine composition showed that spermidine and putrescine were major polyamine components in the parental strain. In the mutant strain, putrescine was replaced by cadaverine. It was found that some polyamines in the cells were conjugated with the other cell components. The growth of the bacterium in the medium below pH 4.5 was inhibited in the presence of α-methylornithine or methylglyoxal-bis(guanylhydrazone), which are inhibitors of rate-limiting enzymes involved in the biosynthesis of polyamines. The growth of the bacterium that had been inhibited in the presence of inhibitors could be fully restored by the addition of putrescine or spermidine. On the basis of these results, it was concluded that polyamines have a significant role in the growth of Acidiphilium facilis 24R under acidic conditions.     

Substantial molecular variation and low genetic structure in Kenya’s black rhinoceros: implications for conservation

Kenya’s black rhinoceros population declined by more than 98% from 20,000 individuals in the 1970s to around 400 individuals in 1990 due to the effects of poaching, at which time the surviving individuals were isolated in a series of demographically inviable subpopulations. An initial management exercise translocated the survivors into four high security sanctuaries to control poaching and enhance breeding, and this measure successfully arrested the decline. Subsequently, new sanctuaries were established and the metapopulation size reached 650 animals by 2008. However, translocations and the current management strategy that partitions the metapopulation into ‘montane’ and ‘lowland’ rhinoceros may have substantial consequences at the population level and their impact on population genetic diversity has not been investigated. In this study, 12 of the 16 extant subpopulations were analysed using 408 bp of mitochondrial control region sequence (n = 170) and nine microsatellite loci (n = 145). Both markers detected moderate to high genetic diversity (h = 0.78 ± 0.027, n = 170; H_O = 0.70 ± 0.087, n = 145) consistent with previous studies on Diceros bicornis michaeli. However, mtDNA and nDNA diversity varied substantially between subpopulations. The results suggest that the Masai Mara is more differentiated, inbred and isolated than other subpopulations. It also suggests that there are neither distinct montane and lowland groups nor other detectable historical barriers to gene flow. Instead the large majority of genetic diversity was partitioned at the level of individuals; highlighting the need to conserve as many individuals as possible. Future translocations should consider the genetic profile of individuals and the demographic history of both the donor and recipient subpopulations.     

Lessons learned developing a diagnostic tool for HIV-associated dementia feasible to implement in resource-limited settings: pilot testing in Kenya

Objective

To conduct a preliminary evaluation of the utility and reliability of a diagnostic tool for HIV-associated dementia (HAD) for use by primary health care workers (HCW) which would be feasible to implement in resource-limited settings.

Background

In resource-limited settings, HAD is an indication for anti-retroviral therapy regardless of CD4 T-cell count. Anti-retroviral therapy, the treatment for HAD, is now increasingly available in resource-limited settings. Nonetheless, HAD remains under-diagnosed likely because of limited clinical expertise and availability of diagnostic tests. Thus, a simple diagnostic tool which is practical to implement in resource-limited settings is an urgent need.

Methods

A convenience sample of 30 HIV-infected outpatients was enrolled in Western Kenya. We assessed the sensitivity and specificity of a diagnostic tool for HAD as administered by a primary HCW. This was compared to an expert clinical assessment which included examination by a physician, neuropsychological testing, and in selected cases, brain imaging. Agreement between HCW and an expert examiner on certain tool components was measured using Kappa statistic.

Results

The sample was 57% male, mean age was 38.6 years, mean CD4 T-cell count was 323 cells/µL, and 54% had less than a secondary school education. Six (20%) of the subjects were diagnosed with HAD by expert clinical assessment. The diagnostic tool was 63% sensitive and 67% specific for HAD. Agreement between HCW and expert examiners was poor for many individual items of the diagnostic tool (K = .03–.65). This diagnostic tool had moderate sensitivity and specificity for HAD. However, reliability was poor, suggesting that substantial training and formal evaluations of training adequacy will be critical to enable HCW to reliably administer a brief diagnostic tool for HAD.     

Acceptability and suitability of Spodoptera exigua (Hübner) for Cotesia icipe Fernandez‐Triana & Fiaboe on amaranth

The beet armyworm Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) is a polyphagous insect that is distributed worldwide and was recently reported as an important pest on African indigenous vegetables. Cotesia icipe Fernandez‐Triana & Fiaboe (Hymenoptera: Braconidae) is a recently described parasitoid, reported from various Afrotropical countries. This work investigated the performance of C. icipe on S. exigua infesting Amaranthus dubius Mart. ex Thell. under laboratory conditions. Cotesia icipe was aggressive on the host and successfully oviposited on S. exigua with 70% of parasitoid females ovipositing after 2 hr of exposure. Parasitoid densities significantly affected the parasitism rate and the nonreproductive larval mortality. Parasitism rate was 9.7 ± 0.8% and 59.5 ± 3.1% for a single and cohort of five females released, respectively, when offered 50 host larvae. The cohort female release resulted in significantly higher larval nonreproductive mortality than the single release. However, there was no significant difference between parasitoid release densities in regard to pupal nonreproductive mortality. The larval and pupal mortalities in the presence of C. icipe were significantly higher than the natural mortalities at both parasitoid release densities. The parasitoid sex ratio was female‐biased for the cohort females but balanced when a single female was released. The hind tibia and forewing lengths were not affected by the density of female parasitoids but there were variations according to sex. The implication of these findings on the potential use of C. icipe for biological control of S. exigua in amaranth production systems is discussed.     

The recent evolution of a pseudogene: diversity and divergence of a mitochondria-localized small heat shock protein in Arabidopsis thaliana

In this study we examined the evolution of the genes for three organelle-localized small heat shock proteins in Arabidopsis thaliana: the chloroplast-localized (CP) protein HSP21 and two mitochondria-localized (MT) proteins, HSP23.5 and HSP23.6. We found that the CP protein and one of the MT proteins, HSP23.6, are evolving under purifying selection to maintain function. In contrast, the gene for HSP23.5, the other MT protein, is highly variable within A. thaliana, and in some accessions or ecotypes this gene may be a pseudogene. HSP23.5 and HSP23.6 are related via a segmental duplication event, and the presence of orthologs of each gene in other species within the Brassicaceae indicates that the duplication generating HSP23.5 and HSP23.6 may have occurred as much as 20 million years ago. This is considerably longer than the 4 million year half-life of gene duplicates (functional genes as well as pseudogenes) reported by some studies. Our results are consistent with the prediction that after gene duplication one gene duplicate can be maintained for some time under relaxed selection while it accumulates random mutations. By capturing a pseudogene in the making our study provides important information on how pseudogenes are formed.     

Ion supply capacity of roots in relation to rejuvenation of primary leaves in vivo

Removal of the shoot above the primary node (detopping) of 3-week-old bean plants ( Phaseolus vulgaris L. cv. Contender) altered the metabolism and development of the remaining leaves. An increase in levels of chlorophyll, protein, stomatal opening, photosynthesis and growth, i.e. rejuvenation of primary leaves, was established within 7 days of detopping. These levels were maintained while the primary leaves of equivalent intact plants senesced.
The flux of xylem solution (mineral ions, cytokinins and water) into leaves is related to the leaf area to be supplied and root supply capacity; it has been suggested that detopping leads to an increased availability of root-supplied solutes and hence rejuvenation of the remaining leaves. This assumes however that root output of solutes is not decreased by the defoliation treatment.
We found that root output of ions (electrical conductivity of passive xylem exudate) in detopped plants was 30% lower than in intact plants after 24 h and 60% lower after 7 days. The output of Ca²⁺, Mg²⁺ and K⁺ were similarly reduced 7 and 14 days after detopping as were fresh and dry weights of roots. Furthermore, neither the calculated xylem flux of ions nor directly measured levels of Ca²⁺, Mg²⁺ and K⁺ were significantly increased in leaves of detopped plants during their rejuvenation. We therefore conclude that root output is tightly coupled to shoot demand and that the apparent rejuvenation of primary leaves caused by detopping bean plants is not a consequence of increased xylem flux of mineral ions into the leaves.     

16S-rRNA-based analysis of bacterial diversity in the gut of fungus-cultivating termites (Microtermes and Odontotermes species)

The interaction between termites and their gut symbionts has continued to attract the curiosity of researchers over time. The aim of this study was to characterize and compare the bacterial diversity and community structure in the guts of three termites (Odontotermes somaliensis, Odontotermes sp. and Microtermes sp.) using 16S rRNA gene sequencing of clone libraries. Clone libraries were screened by restriction fragment length polymorphism and representative clones from O. somaliensis (100 out of 330 clones), Odontotermes sp. (100 out of 359 clones) and Microtermes sp. (96 out 336 clones) were sequenced. Phylogenetic analysis indicated seven bacterial phyla were represented: Bacteroidetes, Spirochaetes, Firmicutes, Proteobacteria, Synergistetes, Planctomycetes and Actinobacteria. Sequences representing the phylum Bacteroidetes (>60 %) were the most abundant group in Odontotermes while those of Spirochaetes (29 %) and Firmicutes (23 %) were the abundant groups in Microtermes. The gut bacterial community structure within the two Odontotermes species investigated here was almost identical at the phylum level, but the Microtermes sp. had a unique bacterial community structure. Bacterial diversity was higher in Odontotermes than in Microtermes. The affiliation and clustering of the sequences, often with those from other termites’ guts, indicate a majority of the gut bacteria are autochthonous having mutualistic relationships with their hosts. The findings underscore the presence of termite-specific bacterial lineages, the majority of which are still uncultured.