Note: Missing Page 57. / Interest on the part of the author in this problem was stimulated by the lack of information about the organism L. monocytogenes, its epidemiology and its ability to grow under certain conditions. There has been great controversy in the past few years, as more data about human Listeriosis became available, about the significance of L. monocytogenes in foetal death and in neonatal disease. There have been reports in the literature, naming L. monocytogenes as a cause of a large percentage of repeated abortions in women in certain areas. Other authors have felt that the importance of L. monocytogenes has been over-estimated.

The ruminant animal, by virtue of the population of active microorganisms which is supported in the rumen, can utilize a much wider range of nitrogen containing substances for body maintenance and production than can the monogastric animal. The rumen microorganisms, chiefly the bacteria, synthesize microbial protein of high biological value from non-protein nitrogen sources in the rumen, and this becomes available to the host animal by normal processes of protein digestion in the abomasum. The animal is therefore not entirely dependent upon dietary protein to satisfy its nitrogen requirements; indeed expansive dietary protein may be conserved by feeding cheaper non-protein supplements to ruminants.

In recent years, the study of antibody synthesis in vitro has aroused considerable interest. Not only does it enable the immunologists to study the phenomenon of antibody formation at a cellular level, free from various factors often associated in a whole body, but also it serves as a model for biochemists in the study of biosynthesis of a specific protein. An antigen is a complex molecule, and very often it contains more than one determinant group that can elicit antibody response. The antibody thus demonstrated in an in vitro system against a microbial antigen cannot necessarily be equated with a measure of immunity against the infection.

In his studies on the isolated cell envelope or a marine pseudomonad, Brown (1960, 1961) observed decreases in the turbidity or suspensions or the cell envelopes when these were incubated at low buffer concentrations. Turbidity changes did not take place when the buffer concentration was increased. These decreases in turbidity or the cell envelope suspensions he interpreted to being due to degradation or the cell envelopes. A number or soluble products were released when the cell envelopes were incubated. The nature or these suggested to Brown that their release was due to the action or an enzyme. Since the release or these compounds was prevented by high buffer concentration, Brown suggested that lysis of the whole cells was due to the action of an enzyme residing in the cell envelope. Prevention of lysis of the whole cells by high salt concentration would then be due to the inhibition by salts of the action of a lytic enzyme.

Nitrogen tantalizes mankind with the paradox of poverty in the midst of plenty. All living things on this planet must have nitrogen in their food. The earth’s atmosphere contains far more than enough nitrogen to satisfy the requirement, yet relatively few of the species populating the earth are able to metabolize nitrogen from the atmosphere. This circumstance gives rise to important ecologic and economic consequences, and poses challenging questions for several branches of science. The first isolation of free living nitrogen fixing bacteria by Winogradsky and Beijernck stimulated attempts to assess the importance of non-symbiotic nitrogen fixation in the nitrogen economy of the soil. Though numerous papers have accumulated, they also provide opportunities for controversy ranging from polite disagreement to acrimonious debate, and most of them need careful reevaluation.

Coumarin (2-oxo-1,2-benzopynpl), a lactone of o-hydroxy-dis-cinnamic acid is a naturally occurring constituent of certain plants, especially sweet clover. Coumarin, present in "spoilt" clover, is sometimes ingested by livestock causing a haemorrhagic condition. Stahmann et al. (1941) identified dicoumarol as the active principle involved. Due to the strong structural relationship of dicoumarol with coumarin, Robert and Link (1937) believed that dicoumarol was formed from coumarin. Many of the coumarin derivatives are pharmacologically active and include anticoagulant drugs, rodenticides and insecticides. Due to its bitter taste and vanilla-like odour, coumarin itself has been employed for flavouring foods but its use has been discouraged owing to its damaging effect on the liver of animals.

By employing Koch's postulates, certain strains of Escherichia coli have been proven to cause enteritis of early weaned pigs. 1. Two strains of hemolytic E. coli were isolated consistently and in large numbers from the fecal samples of early weaned pigs that scoured shortly after weaning. 2. Symptoms of enteritis were reproduced artificially by contaminating the drinking water of the pigs with a live culture of one of the two strains of E. coli. The same strain of E. coli was isolated in very large numbers from the fecal samples of artificially infected animals. 4. The infection of this strain of E. coli was transmitted naturally by housing susceptible animals with the scouring animals. A hypothesis is put forward that certain strains of E. coli occur frequently as part of the normal intestinal microflora of swine and behave as typical infectious agents when suitable conditions for their growth are provided.

Previous work in this department by the present author and others, has demonstrated that changes accompanying the acquisition of resistance to chloramphenicol in Salmonella indicate structural changes in the surface of resistant organisms. Similar changes have been reported by other workers investigating both gram-positive and gram-negative chloramphenicol resistant organisms. The additional observation of a simultaneous increase in resistance to other antibiotics such as penicillin implies a possible non-specific mechanism contributing to resistance linked to the relative permeabilities of the cells. Work was therefore continued with a resistant strain of Salmonella typhimurium in an attempt to find out more about the mechanism of resistance.

Ribonucleic acid (RNA) of tobacco mosaic virus controls the specificity of viral proteins synthesized in the cells of tobacco leaves (Fraenkel-Conrat et al, 1957a) and in a bacterial cell-free system (Taugita et al, 1962). In bacteria, three types of RNA are now recognized, transfer (Berg and Ofengand, 1958), ribosomal (Schachman et al, 1952), and a so-called "messenger” or “rapidly labelled" RNA (Volkin and Astrachan, 1956). The “messenger” fraction is thought to control the specificity of proteins synthesized in bacterial cells (Nomura et al, 1960; Brenner et al, 1961; Gros et al, 1961a; Jacob and Monod, 1961), although direct proof for this claim has not yet been obtained.

The etiology of endemic pneumonia in rats has been investigated, and the specific cause of the condition was established. A viral agent was isolated in rat embryo skin primary tissue cultures, and postulates have been fulfilled for identifying this viral agent with endemic pneumonia in rats. Some characteristics of this virus were established. A method for demonstrating the cytopathogenic agent, involving two-step incubation of inoculated tissue cultures at two different temperatures has been described. This technique was successfully employed for the isolation of the virus responsible for endemic pneumonia in rats.