Noncapsulated Mutant Research Articles

Influence of extracellular polysaccharides on the toxicity of copper and cadmium towardKlebsiella aerogenes

Many investigations have reported the effects of heavy metals on pure cultures of bacteria (14, 21, 30), algae (3, 22, 25), and on natural microbial populations (1, 2, 17). Most of the studies have focused on copper toxicity because copper sulfate has been used as an algicide since the turn of the century (3, 22, 24, 25). The assessment of the toxicity of heavy metals toward microorganisms must take into account the physicochemical parameters of the water (17, 23, 24) and the presence of chelators in natural waters. Natural (humic acids, amino acids, polypeptides) and artificial (EDTA, Nitroloacetate) chelators form organic complexes with metallic ions and thus alter the availability of these toxic metals to aquatic microorganisms (10, 19, 20, 24, 28). Microorganisms are known to produce large quantities of extracellular polysaccharides which are organized in well-defined capsules around the cells, or are excreted as loose materials into the growth medium. The ecological significance of these polymetric materials has been previously discussed (13, 15, 27). However, among the various functions assigned to extracellular polysaccharides, their ability to bind metallic ions has received little attention (11, 26). In this study we report the effect of capsular polysaccharides on copper and cadmium toxicity toward Klebsiella aerogenes. This particular bacterium was chosen because we had a noncapsulated mutant which could be compared to the encapsulated strain.

Filamentous capsulated streptococci from the human respiratory tract. 3. Immunochemical studies of the cross-reactivity between the cell wall antigens of a filamentous streptococcus and of pneumococcus.

A cell wall-associated polysaccharide has been isolated from a noncapsulated mutant, 89R50, of the alpha-hemolytic filamentous streptococcus of provisional capsular type 89. Chemical analysis of the polysaccharide indicates that it consists of galactosamine, glucosamine, glucose, and phosphorus. Immunological cross-reactivity was observed between the streptococcal cell wall antigen and antibody to the cell wall-like capsular polysaccharide of pneumococcus. This cross-reactivity appears attributable to similarities in the teichoic acid moieties rather than in the mucopeptide moieties of the two polymers. No chemical or immunological differences were observed in the cell wall carbohydrate of the noncapsulated streptococcus, 89R50, and that of its capsulated progenitor. It is suggested that antibody to this cell wall polysaccharide might serve as a basis for grouping other filamentous strains of streptococci of diverse capsular types, the cell wall antigens of which show similar cross-reactivity with that of pneumococcus.

Mutation in pneumococcus type 3 affecting multiple cistrons concerned with the synthesis of capsular polysaccharide.

The genetic behavior in transformation reactions of 20 noncapsulated mutants of pneumococcus type III suggests that each has a single-site mutation in the locus controlling the synthesis of uridine diphosphate glucose (UDPG) dehydrogenase. Each strain is capable of yielding transformants of the binary capsular type SI-III when exposed to deoxyribonucleic acid (DNA) from type I cells. One additional mutant reacted differently and behaved as if it were a multisite mutant with the mutation affecting both the locus for UDPG dehydrogenase and that controlling the synthesis of high molecular weight type III capsular polysaccharide. When exposed to DNA from type I pneumococci, this strain yielded transformants which were genotypically binary but which expressed only the type I capsular phenotype.