RESUMEN
A range of isolates of Pseudomonas aeruginosa from widely different environmental sources were examined for their ability to synthesise rhamnolipid biosurfactants. No significant differences in the quantity or composition of the rhamnolipid congeners could be produced by manipulating the growth conditions. Sequences for the rhamnolipid genes indicated low levels of strain variation, and the majority of polymorphisms did lead to amino acid sequence changes that had no evident phenotypic effect. Expression of the rhlB and rhlC rhamnosyltransferase genes showed a fixed sequential expression pattern during growth, and no significant up-regulation could be induced by varying producer strains or growth media. The results indicated that rhamnolipids are highly conserved molecules and that their gene expression has a rather stringent control. This leaves little opportunity to manipulate and greatly increase the yield of rhamnolipids from strains of P. aeruginosa for biotechnological applications.
Asunto(s)
Vías Biosintéticas/genética , Glucolípidos/biosíntesis , Pseudomonas aeruginosa/genética , Pseudomonas aeruginosa/metabolismo , Tensoactivos/metabolismo , Secuencia Conservada , ADN Bacteriano/química , ADN Bacteriano/genética , Microbiología Ambiental , Perfilación de la Expresión Génica , Regulación Bacteriana de la Expresión Génica , Humanos , Datos de Secuencia Molecular , Mutación Missense , Infecciones por Pseudomonas/microbiología , Pseudomonas aeruginosa/aislamiento & purificación , Análisis de Secuencia de ADN , Homología de SecuenciaRESUMEN
Deuterated rhamnolipids were produced using strain AD7 of Pseudomonas aeruginosa, which was progressively adapted to increasing levels of deuterium in D(2)O and carbon substrates. Fourteen different deuterated rhamnolipid structures, including structural isomers, were produced which is similar to normal protonated structures. There were two main products monorhamnolipid Rha-C(10)-C(10) and dirhamnolipid Rha(2)-C(10)-C(10). The levels of deuteration varied from 16% with 25% D(2)O + h-glycerol to 90% with 100% D(2)O + d-glycerol. When d-tetradecane was used with H(2)O, virtually all the deuterium appeared in the lipid chains while using h-tetradecane + D(2)O led to the majority of deuterium in the sugars. The adaptation to growth in deuterium appeared to be metabolic since no genetic changes could be found in the key rhamnolipid biosynthetic genes, the rhamnosyl transferases RhlB and RhlC. Deuterated sophorolipids were similarly produced using Candida bombicola and Candida apicola although in this case, no adaptation process was necessary. Up to 40 different sophorolipids were produced by these yeasts. However, unlike the rhamnolipids, use of D(2)O did not lead to any deuteration of the lipid chains, but direct incorporation into the lipid was achieved using d-isostearic acid. The results from these experiments show the feasibility of producing deuterated bioactive compounds from microorganisms coupled with the possibility of manipulating the pattern of labelling through judicious use of different deuterated substrates.