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171.
IST1 insertional inactivation of the resB gene: implications for phenotypic switching in Thiobacillus ferrooxidans 总被引:1,自引:0,他引:1
Maria-Eugenia Cabrejos Hui-Ling Zhao Maritza Guacucano Susan Bueno Gloria Levican Emilio Garcia Eugenia Jedlicki David S Holmes 《FEMS microbiology letters》1999,175(2):223-229
Thiobacillus ferroxidans ATCC 19859 undergoes rapid phenotypic switching between a wild-type state characterized by the ability to oxidize ferrous iron (FeII) and reduced sulfur compounds and a mutant state where it has lost the capacity to oxidize FeII but retains the ability to oxidize sulfur. The mutant has also gained the capacity to swarm. It is proposed that loss of FeII oxidation is due to the reversible transposition of the insertion sequence IST1 into resB encoding a putative cytochrome c-type biogenesis protein. Downstream from resB and co-transcribed with it is resC, encoding another putative cytochrome biogenesis protein. IST1 insertional inactivation of resB could result in the loss of activity of its target c-type cytochrome(s). This putative target cytochrome(s) is proposed to be essential for FeII oxidation but not for sulfur oxidation. Curiously, resB and resC pertain to the proposed system II cytochrome biogenesis pathway whereas gamma Proteobacteria, of which T. ferrooxidans is a member, normally use system I. This could represent an example of lateral gene transfer. 相似文献
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Maritza Alarcn Cesare Colasante Sonia Araújo Reinaldo Gutirrez-Marín Dalmiro Cazorla-Perfetti Claudia Magaly Sandoval-Ramírez 《Biomédica : revista del Instituto Nacional de Salud》2021,41(1):179
IntroducciónBelminus ferroae es un triatomino de comportamiento entomófago, sin embargo, puede alimentarse de vertebrados ocasionalmente. No se ha demostrado infección natural por Trypanosoma cruzi en esta especie, como tampoco la metaciclogénesis del parásito.ObjetivoExaminar la metaciclogénesis de T. cruzi en B. ferroae y la capacidad infectiva de las heces o sus contenidos intestinales en roedores.Materiales y métodosSe analizaron las heces y la orina expulsadas espontáneamente por los insectos o mediante compresión abdominal o extracción del contenido intestinal a los 10, 20, 30, 40, 50 y 60 días. Se cuantificó la carga parasitaria de T. cruzi y sus formas evolutivas se identificaron con tinción de Giemsa. Asimismo, se evaluó en ratones albinos la capacidad infectiva de los tripomastigotes metacíclicos de T. cruzi obtenidos de las heces o contenidos intestinales de los especímenes infectados.ResultadosEl análisis parasitológico reveló tres (15%) insectos infectados con T. cruzi a los 30 (n=1), 40 (n=1) y 50 (n=1) días después de la infección con cargas parasitarias de hasta 1,62 x 105 tripanosomas/mm3 y porcentajes de metaciclogénesis entre el 3,5 y el 6,78%.ConclusionesSe demuestra por primera vez, en una especie del género Belminus. la metaciclogenésis de T. cruzi en condiciones de laboratorio y la capacidad infectiva de las heces para un huésped vertebrado.Palabras clave: Trypanosoma cruzi, Triatominae, enfermedad de Chagas, tripanosomiasis 相似文献
175.
Marc Sporleder Erica Maritza Rodriguez Cauti Jürg Huber Jürgen Kroschel 《Agricultural and Forest Entomology》2007,9(4):271-278
1 Granulovirus PoGV is a strong candidate to substitute for chemical insecticides in integrated pest management (IPM) of the potato tuber moth Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae). Generally, susceptibility to baculoviruses decreases with increasing larval age. For effective field applications, knowledge of the age‐related change in susceptibility is crucial. 2 The relative susceptibility of various instars of P. operculella larvae to PoGV was studied by leaf‐disc bioassays in the laboratory at 26 °C incubation temperature. The LC50 increased from 4 × 106 granules/mL for neonate larvae to 1.2 × 107, 1.1 × 108, 4.4 × 108, and 4.2 × 109 granules/mL, signifying resistance ratios of 3, 29, 110, and 1051, for 5, 6, 7, and 9‐day‐old larvae, respectively. 3 The relationship between log‐LC50 values and log‐larval weight was significantly linear. A logistic function described significantly the relation between larval weights and physiological age measured in degree‐days (DD > 13.4 °C). Both functions allowed prediction of the activity ratio of PoGV for different larval ages by using temperature summation to express physiological age. 4 PoGV was found to be highly active against P. operculella larvae up to a physiological age of approximately 50 DD (>13.4 °C) (i.e. the first third of the total larval development time). Thereafter, the virus rapidly lost its activity against older larvae. Prospects for applying this knowledge in the field are discussed. 相似文献