RESUMO
Flocculation is a very useful phenotype for industrial yeast strains, since it facilitates cell harvest and represents an easy way of cell immobilization in continuous fermentation processes. The present work represents the first time that an inducible flocculation phenotype has been generated in a non flocculent strain of Kluyveromyces marxianus. This was accomplished by expressing Saccharomyces cerevisiae FLO5 gene in K. marxianus CECT 11769 strain. The FLO 5 gene was placed under the control of an EPG promoter, not repressed by glucose and induced by anoxia. Our experimental approach successfully generated two novel K. marxianus flocculent phenotypes: one inducible and one constitutive. The constitutive phenotype originated from deletions in the FLO5 promoter region, indicating the existence of putative upstream repressor site involved in oxygen regulation of the EPG1 promoter. The novel strains here generated had a unique set of characteristics that provided an advantage, over the wild-type strain, for the industrial co-production of ethanol and polygalacturonase.
RESUMO
Introducción: Bacillus cereus es una bacteria Gram positiva, habitante frecuente de un amplio número de ambientes. Esta bacteria es la responsable del síndrome emético y del diarréico, y además se ha identificado vinculada a otras enfermedades como endocarditis, endoftalmitis, por lo que se le reconoce su carácter de patógeno oportunista. Objetivo: revisar información sobre las toxinas producidas por B cereus y cuáles y cómo están relacionadas con las intoxicaciones alimentarias, así como abordar otros factores responsables de la virulencia de esta bacteria. Fuente de datos: para recopilar la información necesaria se utilizó el acceso a Internet mediante los buscadores Google y Scirus. Los artículos que se examinaron incluyeron revisiones del tema, artículos de investigación y capítulos de libros extraídos como acceso libre o solicitados a los autores. Síntesis de los datos: se profundizó en el conocimiento sobre la toxina emética y la diarreica, la sintomatología clínica, el tiempo de aparición, así como los alimentos involucrados en cada síndrome, lo cual sirve de ayuda al clínico para determinar las causas de la toxoinfección. Se hace un bosquejo general de la microbiología de esta bacteria y otros factores que explican su virulencia y otras implicaciones en la salud humana. Conclusiones: El conocimiento obtenido permite reconocer a B. cereus como una bacteria con importancia clínica, lo que evita considerarla solo como un contaminante ambiental
Introduction: Gram positive bacterium Bacillus cereus is widely distributed in the environment. This bacterium is responsible for two food poisoning syndromes (emetic and diarrheal) and also it has been related to other diseases such as endocarditis and endophthalmitis; therefore it is recognized as opportunist pathogen. Objective: to review the information about Bacillus cereus toxins and its connection with food poisoning, as well as to address others factors influencing this bacterium's virulence. Data sources: for collecting this information, search engines such as Google and Scirus. Reviewed articles included research articles, systematic reviews on this topic and free accessed book chapters, or requested from the authors. Data synthesis: the review delved into Knowledge on diarrheal and emetic toxins, clinical symptomatology and time of occurrence, as soon as foodstuffs involved in each syndrome. This helps the clinician to look for the causes of toxin infections. A general overview of Bacillus cereus microbiology and others factors that explain its virulence and other implications in the human health was given. Conclusions: the acquired knowledge shows that Bacillus cereus is one bacterium with clinical importance rather than a mere environmental pollutant