Conductimetric assessment of the biomass content in suspensions of immobilised (gel-entrapped) microorganisms

Summary The problem of obtaining a rapid estimate of the microbial content of an immobilised cell suspension is addressed. The low-frequency conductivity of free-living cell suspensions of Clostridium pasteurianum is lower than that of the medium in which they are suspended, by an amount conforming to the Bruggeman relation. The conductivity of the cell wall makes a negligible contribution to the measured conductivity under the conditions used. Calcium alginate beads (lacking microbial cells) lower the conductivity of a solution with which they have been equilibrated by an extent which is a function of the concentration of alginate gel used in forming the beads. When this is taken into account, the ratio of the conductivity of a suspension of gel-immobilised cells to that of the suspending medium can be used to give a rapid and convenient assessment of the amount of microbial biomass present.     

Chicken lens delta-crystallin gene expression and methylation in several non-lens tissues.

RNA sequences coding for the most abundant chicken lens proteins, delta-crystallin, were detected at very low levels in day old post hatch chick lung, heart, kidney and liver, and in 6 day embryo headless bodies. The pattern of cytosine methylation within the CCGG sequences of the delta-crystallin genes was also examined and shown to vary in several non-lens tissues, from several stages of development. Embryonic neural retina, which expresses a higher level of delta-crystallin RNA than the above tissues, is no less methylated in the sites studied than the tissues which have no association with the eye, and is actually more heavily methylated than the kidney. Thus no obvious correlation was found between undermethylation and gene expression.     

A mass-spectrometric sequence study of the enzyme ribitol dehydrogenase from Klebsiella aerogenes

The first detailed results of the application of a low-resolution mixture analysis approach to the sequence analysis of an enzyme, ribitol dehydrogenase, are given. Examples of the interpretation of the spectra of peptide mixtures derived from this protein are described. Evidence for new fragmentation patterns observed is reported, together with an explanation of the generation of ambiguous sequences by use of a low-specificity enzyme, thermolysin. The overall sequencing strategy evolved is assessed.     

Metabolism of Glutamic Acid and N-Acetylglutamic Acid in Leaf Discs and Cell-free Extracts of Higher Plants

Radioactive glutamic acid and N-acetylglutamic acid have been incubated with normal and wilted leaf discs and radioactivity recovered in uncombined proline. The discs which had been placed under moisture stress incorporated considerably more label in uncombined proline than did normal discs.     

Properties of the inactive ribosomal components in rat liver and hepatoma

1. The relative concentrations of the inactive ribosomal components were compared in normal and regenerating rat liver and in two transplantable rat hepatomas (hepatomas 7800 and 5123D). 2. The size of the ribosomal-subunit pools in normal liver was not significantly affected by partial hepatectomy or neoplasia although, as shown previously, significant changes do occur in the monomer pool. 3. Further, the subunit pools in both liver and hepatoma were not significantly influenced by several treatments that caused dramatic changes in the size of the ribosomal monomer (and dimer) pools. 4. The high concentration of inactive monomers and dimers in the hepatomas appears to arise from limitations at the translational level, since they can be incorporated into pre-existing polyribosomes under the influence of cycloheximide.