- Volume 125, Issue 1, 1981

Binding sites of Escherichia coli RNA vmerase on RP4 plasmid DNA were determined electron microscopically. Comparison RNA polymerase binding map and the genetic map of RP4 revealed several strong sites outside the well-known RP4 genes. RNA polymerase binding sites for the three tic resistance genes were also detected. Two binding sites were observed for the tra-on, whereas the tra-2 and tra-3 regions showed no prominent affinity for RNA polymer. The genomic regions for the replication origins, oriV (for vegetative replication) and for transfer replication, equivalent to rlx), both exhibited strong binding to RNA ase, as did genomic regions which code for trans-acting replication functions (trfAB).

The efficiency of plating of Escherichia coli K12 and its derivatives K12 C600 and K12 C600(λ) is diminished during the transition period from the lag to the exponential growth phase in cultures grown in tryptone broth. The phenomenon is suppressed in cultures of the strain K12 C600(λind). The reduction in the efficiency of plating is transitory and not influenced by temperature between 30 and 42 °C.

A simple, convenient method of growing large quantities of Candida albicans chlamydospores on a cellulose dialysis membrane has been developed. Long, narrow, cylindrical suspensor cells bearing spherical to ovoid chlamydospores were observed. Ultrastructural observations showed the chlamydospore to have a bilayered cell wall made up of an outer electron-transparent primary layer and an inner electron-dense secondary layer, a large portion of the total cell volume occupied by a single large vacuole and several smaller vacuoles, and cytoplasmic organelles typical of those observed in the yeast-like cell. There are structural similarities between the region of chlamydospore-suspensor cell connection and septa observed in budding yeast-like cells.

A test for susceptibility to 5-fluorouracil was useful for differentiating between species of rapidly growing mycobacteria, and for differentiating the genus Rhodococcus from the genus Nocardia. The majority of rhodococci tested were susceptible to 5-fluorouracil (20 μg ml−1), whereas the majority of nocardiae tested were resistent to it. Strains of Nocardia asteroides sensu stricto could be divided into two subgroups by their reaction to 5-fluorouracil.

In Saccharomyces cerevisiae, Neurospora crassa, Aspergillus nidulans and Coprinus cinereus most of the alkali-insoluble (1→3)-β-D/(1→6)-β-d-glucan of the wall can be extracted with dimethyl sulphoxide. The same fraction, and in Saccharomyces cerevisiae a small additional fraction, can be extracted by a destructive procedure involving 40% NaOH at 100 C. The small fraction of the glucan which resists this treatment becomes soluble after a subsequent treatment with HNO2 indicating that it is covalently linked to chitin in the wall. In contrast, in Schizophyllum commune and Agaricus bisporus, nearly all the (1→3)-βD-/(1→6)β-d-glucan appears to be held insoluble by linkage to chitin.

During prolonged static cultivation of liquid cultures of Salmonella strains with normal flagella, flagellar shape mutants occurred spontaneously and their proportion in the cultures increased so that they were easily isolated by spreading dilutions of the cultures on semisolid medium. By this method various types of flagellar shape mutants, including curly, straight and polymorphous mutants, were obtained.

Spontaneous alginate-producing (muc) variants were isolated from strain of Pseudomonas fluorescens, P. putida and P. mendocina at a frequency of 1 in 108 by selcting for carbenicillin resistance. The infrared spectrum of the bacterial exopolysaccharide was typical of an acetylated alginate similar to that previously described in Azotobacter vinelandil and in mucoid variants of P. aeruginosa. Mucoid variants were not isolated from P. stuteri, P. pseudoalcaligenes, P. testosteroni, P. diminuta, P. acidovorans, P. cepacia or P. maltophilia.