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Homoserine inhibited fluorescent phytopathogenic pseudomonads of the Pseudomonas syringae group. An intermediate in a branched pathway of amino acid biosynthesis, homoserine was not toxic in the presence of the pathway's end products, methionine, threonine and lysine. Various inhibitions in four branched biosynthetic pathways by certain amino acid end products, in the absence of others, lead to cessations of growth of phytopathogenic strains representing P. coronafaciens var. atropurpurea, P. glycinae, P. helianthi, P. mori, P. phaseolicola, P. syringae and P. tabaci. Saprophytic strains representing P. fluorescens and P. putida were only inhibited by cysteine, an inhibitor of all the strains studied. Conditions of free amino acid imbalances, as exist in plants, may lead to inhibitions of these pathogens and may in some instances determine their range of compatible hosts and tissues.

Production of carbohydrases by Alternaria solani is inhibited by glucose under low growth conditions. In an enriched medium, glucose has little effect on the production of polygalacturonase and cellulase while it still suppresses production of β-glucosidase. Low levels of all three enzymes were produced in the absence of their respective substrates. Such regulation has been found with many organisms. However, far greater production of these carbohydrases occurred with additions of adenosine phosphates to the growth media. Highest stimulation of enzyme production was by adenosine 5′-phosphate. Adenosine 5′-triphosphate and cyclic 3′, 5′-adenosine monophosphate gave lesser amounts. Starvation appears to induce production of extracellular carbohydrases and adenosine 5′-phosphate may have a role in the starvation process.

The mycotoxin patulin inhibits germination of apple pollen in vitro, and the growth of cultured soybean cell suspensions. Patulin inhibits pollen respiration by 50%. In soybean cultures both salicylhydroxamic acid (SHAM), an inhibitor of the cyanide-insensitive mitochondrial electron transport which is alternative to cytochrome electron transport, and patulin inhibit respiration 50–60%. In contrast KCN stimulates soybean cell respiration. Patulin and SHAM appear to compete for the same site(s) of inhibition since patulin is not as inhibitory when respiration is previously inhibited by SHAM. Patulin inhibits the entry of phenylalanine and threonine into soybean cells. Phenylalanine transport appears to be energy coupled since it is inhibited by the uncoupler 2,4-dinitrophenol (DNP) and by a combination of the respiratory inhibitors KCN plus SHAM.

Manure disposal can be a serious environmental problem in poultry-cage facilities for egg production. Flies can degrade manure and they offer a possibility of recycling products. All flies studied were inadequate to degrade accumulattons of anaerobic manure. Among several species of muscoid flies tested Musca domestica L. was most effective in degrading aerobic manure. Different strains thrived in manure variously according to their general vigor. Poultry manure provides an adequate source of protein for egg maturation for M. domestica and it is a suitable oviposition medium except when a more attractive medium is present. Manure is an adequate medium for maggot culture, although of lower quality than a standard medium; its quality diminishes with age. As manure is biodegraded, metabolic activity of contained organisms increases to a plateau, ammonia is produced, nitrogen is lost, and p H increases. Bacteria, rather than fungi and yeasts, are primarily responsible for these changes, but metabolism of bactcria and developing maggots interact. Some bacteria may retard fly development. Fly larvae perform a conspicuous role in aerating medium to favor aerobic bacteria and to hasten loss of nitrogen and moisture. The design of batch or continuous systems of manure degradation by flies should include developmental and behavioral characteristics of insects appropriate to the system.

Regulation of pectate lyase synthesis was examined in Erwinia and Pseudomonas species. Soft rot bacteria produced 100- to 1000-fold more enzyme per cell under optimal conditions than did other bacterial pathogens or saprophytes. Among pseudomonads, only Pseudomonas marginalis and a few other fluorescent strains isolated from plant tissue synthesized pectate lyase. Constitutive synthesis was common in this group. In contrast, lyase synthesis in most Erwinia species examined was inducible. Polypectate and pectin were effective carbon sources for lyase induction in some Erwinia strains while other strains showed much higher inducible synthesis on pectin than on polypectate. Vegetable extracts had profound effects on lyase synthesis. Potato extract, which was previously reported as exerting a synergistic effect on induction of pectate lyase in Erwinia carotovora ATCC 8061 grown on pectin, repressed lyase synthesis in other Erwinia strains. At high concentrations, extracts of carrot, lettuce and onion severely repressed constitutive and inducible synthesis. At low concentrations, lettuce and onion extracts stimulated constitutive lyase synthesis in Pseudomonas marginalis . The wide variety of regulatory controls governing lyase synthesis and the repressive as well as synergistic effects of vegetable extracts on synthesis suggest that the etiology of bacterial soft rot diseases can be influenced by such regulatory mechanisms.