Nephelometric and turbidometric assays of cellulase activity

Extensively ball-milled cellulose fibers were used as natural substrate for the determination of cellulase activity. This physical treatment breaks the large cellulose fibers to small but insoluble particles yielding a substrate accessible for complete enzymatic breakdown. The parameters studied to estimate the activity of cellulases were (a) the decrease in optical density of ball-milled suspension of fibers and (b) simultaneous measurement of liberated sugars during hydrolysis. A good correlation was found between the initial rate of reaction and the amount of sugar released at given times.     

Nephelometric density adjustment of leptospiral antigen.

In testing leptospirosis by microagglutination, reproducibility of the results is affected by population age and germ concentration. These undesirable factors can be avoided if antibody identification is made with cultures incubated for 7 to 21 days and adjusted to 50 X 10(6) leptospires per mililitre. Most suitable for the purpose is an analogue mode based on nephelometry and the probability theory. The obtained statistical data furnish calculated and tabulated apparatus values which are used for standardizing with the aid of a newly developed nepheloflask with compression-spring stirrer.     

Nephelometric determination of turgor pressure in growing gram-negative bacteria.

Gas vesicles were used as probes to measure turgor pressure in Ancylobacter aquaticus. The externally applied pressure required to collapse the vesicles in turgid cells was compared with that in cells whose turgor had been partially or totally removed by adding an impermeable solute to the external medium. Since gram-negative bacteria do not have rigid cell walls, plasmolysis is not expected to occur in the same way as it does in the cells of higher plants. Bacterial cells shrink considerably before plasmolysis occurs in hyperosmotic media. The increase in pressure required to collapse 50% of the vesicles as external osmotic pressure increases is less than predicted from the degree of osmotically inducible shrinkage seen with this organism or with another gram-negative bacterium. This feature complicates the calculation of the turgor pressure as the difference between the collapse pressure of vesicles with and without sucrose present in the medium. We propose a new model of the relationship between turgor pressure and the cell wall stress in gram-negative bacteria based on the behavior of an ideal elastic container when the pressure differential across its surface is decreased. We developed a new curve-fitting technique for evaluating bacterial turgor pressure measurements.     

Relatedness between the coagulase gene 3'-end region and coagulase serotypes among Staphylococcus aureus strains

The 3'-end region of the coagulase gene from 22 strains of Staphylococcus aureus including 10 standard serotype strains was sequenced, and five subgroups with 4-8 tandem repeating units were distinguished among the tested strains. Phylogenetic analysis of the 3'-end region of the coagulase gene indicated that strains belonging to the same serotype were clustered in the same branch. A phylogenetic tree of the deduced amino acid sequences revealed that the C-terminal region might not be responsible for the epitope of the coagulase protein.     

Nephelometric parameters of plasmolytic reactions in Escherichia coli K-12

Nephelometric parameters of plasmolysis in Escherichia coli K-12 are presented. The relationship between these parameters and intracellular osmotic pressure, barrier properties of the cytoplasmic membranes and transport of inorganic ions was investigated in the present work. The nephelometric parameters can be used for quantitative estimation of the physiological state of the bacteria.