Citrobacter freundii as a test platform for recombinant cellulose degradation systems.

Cellulosic biomass represents a huge reservoir of renewable carbon, but converting it into useful products is challenging. Attempts to transfer cellulose degradation capability to industrially useful micro-organisms have met with limited success, possibly due to poorly understood synergy between multiple cellulases. This is best studied by co-expression of many combinations of cellulases and associated proteins. Here, we describe the development of a test platform based on Citrobacter freundii, a cellobiose-assimilating organism closely related to Escherichia coli. Standard E. coli cloning vectors worked well in Cit. freundii. Expression of cellulases CenA and Cex of Cellulomonas fimi in Cit. freundii gave recombinant strains which were able to grow at the expense of cellulosic filter paper or microcrystalline cellulose (Avicel) in a mineral medium supplemented with a small amount of yeast extract. Periodic physical agitation of the cultures was highly beneficial for growth at the expense of filter paper. This provides a test platform for the expression of combinations of genes encoding biomass-degrading enzymes to develop effective genetic cassettes for degradation of different biomass streams. SIGNIFICANCE AND IMPACT OF THE STUDY: Biofuels have been shown to be the best sustainable and alternative source of fuel to replace fossil fuels. Of the different types of feedstocks used for producing biofuels, lignocellulosic biomass is the most abundant. Converting this biomass to useful products has met with little success. Different approaches are being used and microbial platforms are the most promising and sustainable method. This study shows that Citrobacter freundii is a better test platform than Escherichia coli for testing various combinations of cellulases for the development of microbial systems for biomass conversion.

Endometriosis of the urinary bladder.

Although every seventh or eighth case of endometriosis is found to have urinary involvement, this type of endometriosis is still rarely recognized. The symptoms are not specific and are frequently suggestive of a neoplastic process. On the basis of our two cases of histopathologically two types of endometriosis as well as literature review the practical significance of endometriosis in urology is described. In each patient who previously underwent a gynaecological or surgical procedure in the abdominal cavity, endometriosis of the bladder is likely to occur. This possibility should not be ruled out, otherwise it could lead to misdiagnosis and inappropriate treatment.

Variability in the susceptibility pattern of Bacteroides fragilis in four Detroit area hospitals.

Recent clinical isolates of Bacteroides fragilis selected at random from four Detroit area hospitals were collected over a 3-month period, and the minimum inhibitory concentrations were determined within several days. The levels of antimicrobial agents used in this survey breached the concentration attainable in the patient's serum. The antimicrobial susceptibility patterns of these isolates to five antimicrobial agents suggest that there is a 20% variation in the resistance to clindamycin and also up to 20% variation among the other four antibiotics in the four area hospitals. The changing susceptibility pattern of B. fragilis to antibiotic resistance suggests that minimum inhibitory concentrations should be determined for all isolates from serious clinical infections.