A commercial strain of Streptococcus thermophilus possessing galactokinase activity was examined for the effect of lactose flow rate on the production and composition of polysaccharides through the early steps of biosynthesis. In all cases, lactose-grown cells did not release free galactose into the medium and produced polysaccharides containing galactose, glucose, mannose, uronic acids and minor amounts of hexosamines. In batch cultures with excess lactose present the cells converted nearly 80% of the carbon source to L-lactate and produced 2.4g 1-1 (eq. glucose) polysaccharides. However, when the carbon flow was set at 1.5 mM h -a, only 47% of the fermented sugar was converted to Llactate by the strain, which synthetized 22% more polysaccharides. As lactose became limiting, the level of some glycolytic enzymes and nucleotidyltransferases markedly decreased while phosphoglucomutase, phosphomannose isomerase and galactokinase activities were stimulated. The shift in the key enzyme ratios was reflected by major changes in polysaccharide distribution, which definitely altered in favour of galactose. Data suggested a diversion of lactose flow towards polysaccharide production at the expense of lactic acid and biomass formation, as well as a fine regulation of polymer distribution when the cell growth of S. thermophilus was limited by the carbon source feed rate.
Assimilation of ammonium by the obligate anaerobic bacterium Closlridium acetobufylicirm was accomplished by the pathway: Glutamine synthetase/glutamate synthase. C. ace/ohutylicum also contained an asparagine synthetase, but no glutamate dehydrogenase activity was detected. The glutamine synthetase was partially repressed by addition of large amounts of ammonium chloride and/or casaminoacids to the medium, while the biosynthesis of the other enzymes was not regulated by the extracellular concentration of ammonium.In all biological systems, the assimilation of nitrogen into macromolecules is essential for growth. (BOGDAHN and KLEINER 1986). Comparative investigations showed marked differences in the properties of enzymes involved in the inorganic nitrogen assimilation. Thus, the reductive amination of a-ketoglutarate by glutamate dehydrogenase is the most commonly occurring pathway in microorganisms although this enzyme is not detected in some N,-fixing bacteria like C. pasteurianum (KLEINER 1979) and Aiotohacter vinelatdii (KLEINER 1975).The glutamine synthetase/glutamate synthase system was demonstrated to operate in C. pasteiirimum according to the following pathways (DAINTY and PEEL 1970) :Glutamine synthetase is the key enzyme of this pathway, modulating the flow of NH; and catalyzing the biosynthesis of glutamine, a compound of central importance in nitrogen metabolism ( STADTMAN 1973).In this paper, we report analogous investigations on the pathway of ammonium assimilation by Clostridium acetohutylicum. Materials and methodsMicroorganism : Clostridium acetohutylicttrn ATCC 824 was maintained on "Reinforced Clostridial Medium" (R.C.M., OXOID Ltd.) at 35 "C for 5 days followed by storage at 4 "C. For inoculum preparation, the culture
Background: Maturity-onset diabetes of the young (MODY) is a monogenic form of diabetes characterized by autosomal dominant inheritance. To offer an adequate patient management and therapeutic treatment for MODY patients, in addition to an early efficient diagnosis of their asymptomatic relatives, it is crucial to set an accurate molecular diagnosis. Hence, our aim was to determine the frequency of HNF1A and GCK genes among Moroccan-suspected MODY patients. Methods: Twenty suspected MODY patients were screened for HNF1A and GCK mutations using Sanger sequencing and MLPA methods. Segregation analysis of identified mutations was performed among family members. The pathogenic nature of missense variants was predicted using bioinformatic tools. Results: A total of two mutations were revealed among all patients raising the diagnostic rate to 10%. We identified a large novel GCK deletion (c.209-?_1398+?del) by MLPA in one patient and a previously reported missense substitution (c.92G > A) in HNF1A gene. Conclusion: This is the first investigation to perform the molecular diagnosis of MODY suspected patients. Our findings constitute a primary contribution towards unraveling the genetic landscape involved in the pathogenesis of MODY disease in Morocco.
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