PubMed · 3603007
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B R Jones, E M Leise. 1987-06-26. Neuronal circuits and evolution.. https://doi.org/10.1126/science.3603007
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We present the first genome-wide study of recent evolution in Culex pipiens species complex focusing on the genomic extent, functional targets and likely causes of global and local adaptations. We resequenced pooled samples of six populations of C. pipiens and two populations of the outgroup Culex torrentium. We used principal component analysis to systematically study differential natural selection across populations and developed a phylogenetic scanning method to analyse admixture without haplotype data. We found evidence for the prominent role of geographical distribution in shaping population structure and specifying patterns of genomic selection. Multiple adaptive events, involving genes implicated with autogeny, diapause and insecticide resistance were limited to specific populations. We estimate that about 5-20% of the genes (including several histone genes) and almost half of the annotated pathways were undergoing selective sweeps in each population. The high occurrence of sweeps in non-genic regions and in chromatin remodelling genes indicated the adaptive importance of gene expression changes. We hypothesize that global adaptive processes in the C. pipiens complex are potentially associated with South to North range expansion, requiring adjustments in chromatin conformation. Strong local signature of adaptation and emergence of hybrid bridge vectors necessitate genomic assessment of populations before specifying control agents.
The presence of dormant tubercle bacilli presents a major problem for tuberculosis treatment. The culture supernatant of Mycobacterium tuberculosis was previously shown to resuscitate dormant bacilli in vitro. Here we report identification of active components as phospholipids and a tuberculosis protein Rv1174c. Remarkably, dormant bacilli from a one year old culture which failed to form any colonies could be resuscitated with peptides derived from Rv1174c and formed 10(5-7) colonies/ml. This finding represents the first unambiguous demonstration of resuscitation of dormant tubercle bacilli in vitro and may have implication for the study of mycobacterial dormancy and the design of novel strategies for improved treatment of tuberculosis.
Inorganic polyphosphate (polyP) has been identified and measured in different stages of Trypanosoma cruzi. Millimolar levels (in terms of P(i) residues) in chains of less than 50 residues long, and micromolar levels in chains of about 700--800 residues long, were found in different stages of T. cruzi. Analysis of purified T. cruzi acidocalcisomes indicated that polyPs were preferentially located in these organelles. This was confirmed by visualization of polyPs in the acidocalcisomes using 4',6-diamidino-2-phenylindole. A rapid increase (within 2--4 h) in the levels of short and long chain polyPs was detected during trypomastigote to amastigote differentiation and during the lag phase of growth of epimastigotes (within 12--24 h). Levels rapidly decreased after the epimastigotes resumed growth. Short and long chain polyP levels rapidly decreased upon exposure of epimastigotes to hypo-osmotic or alkaline stresses, whereas levels increased after hyperosmotic stress. Ca(2+) release from acidocalcisomes by a combination of ionophores (ionomycin and nigericin) was associated with the hydrolysis of short and long chain polyPs. In agreement with these results, acidocalcisomes were shown to contain polyphosphate kinase and exopolyphosphatase activities. Together, these results suggest a critical role for these organelles in the adaptation of the parasite to environmental changes.