Obligate anaerobic bacteria isolated from the intestinal tracts of the freshwater fish Tilapia and identified as the genus Bacteroides were separated into two groups at the species level (Bacteroides ATS and BTS) according to morphological and physiological properties. The two groups are significantly different in NaCl requirement, optimal growth temperature, pH, metabolic products, and antibiotic susceptibility. They have little ability to degrade macromolecular compounds, except for some strains which hydrolyzed the starch or chitin. Bacteroides ATS was predominant in the intestines of all species of Tilapia throughout their lives, but Bacteroides BTS tended to increase in accordance with fish growth to a level similar to that of Bacteroides ATS.
As HOU et al. (1, 2) mentioned, cell-free extract from methanol-grown yeasts catalyzes the oxidation reaction of secondary alcohols to methyl ketones. Recently, we found that glucose-grown yeasts also produce secondary alcohol dehydrogenase that is constitutively formed. Among several methanol-grown yeasts, Hansenula polymorpha P-5 was the most suitable enzyme source because of its thermal stability and broad substrate specificity. In addition to the secondary alcohols, primary alcohols and 1, 2-propanediol are also oxidized by the cell-free extract of H. polymorpha P-5. The oxidation of secondary alcohols to methyl ketones by immobilized yeast cells was examined and compared with the oxidation by the cell suspensions. Oxygen was essential for the conversion of 2-propanol to acetone. The secondary alcohol dehydrogenase activity of the immobilized cells was not affected by pH shock from 7.0 to 3.5, but with the cell suspension it was affected. The optimun pH for the cell suspension was about 8.5, but the immobilized yeast cells had a broad optimum pH range from 5.0 to 8.5. Only an 8% decrease in the enzyme activity of the immobilized yeast cells occurred when the pH was below 4.0. For the immobilized yeast cells, the tolerance concentration of the secondary alcohol dehydrogenase to acetone was up to 5% (v/v). However, with cell suspensions, the enzyme was not tolerant to acetone. The optimal enzyme activity of cell suspensions lasted 2 days; that of immobilized yeast cells lasted 3 days. The enzyme activity of immobilized cells could be restored with glucose medium.
The effect of media composition on the selection of different components of a mixed microbial population during serial transfer was examined. The initial microbial populations were from the small intestinal contents of 3- and 8-day-old piglets. Selection in brain-heart infusion broth was compared with selection in media based on piglet diets, either piglet feed infusion or sow colostrum. Clostridium and Lactobacillus were the predominant organisms isolated from media prepared from sow colostrum and piglet feed, although the microflora from piglet feed infusion broth was more varied and complex. Lactobacillus and non-hemolytic Escherichiacoli were the predominant organisms identified from brain-heart infusion broth. Nearly half (48%) of the microflora from brain-heart infusion broth originally inoculated with intestinal fluid from an 8-day-old piglet consisted of non-hemolytic E. coli. E. coli were not detected after serial transfer in either sow colostrum or piglet feed infusion broths. Absence of E. coil was attributed in part to the presence of inhibitory substance(s) in sow colostrum and piglet feed infusion broths and in part to the presence of organisms antagonistic to E. coli. Bifidobacterium A, Clostridium F, and Lactobacillus F, which comprised 24% of the isolates obtained after serial transfer in sow colostrum broth, were antagonistic toward E. coil as well as were Bifidobacterium C, Lactobacillus G, and Leptotrichia A, which accounted for 38% of the isolates obtained after serial transfer in piglet feed infusion broth.
Adsorptive phenomena involving Escherichia coli and an anion exchange resin, Dowex 1 in chloride form, were studied in terms of three categories; attachment, loose immobilization and repulsion. Attachment was directly quantified, but the latter two were estimated by the ratio between cell concentrations in the inter-particle space in resin sediment (Cr) and in the supernatant (Cl). Attachment was accompanied by proportional desorption of chloride ions. Attachment and loose immobilization with unmodified and modified cells were affected by pH, suggesting that the number and dissociation balance of anionic and cationic groups of bacterial surface are involved in both of them. Attachment of more cells became difficult with the increase in attached cell density. This was attributed to the repulsion between free and attached cells. When cell concentration in bulk solution was not so high, the repulsion varied with the amount of attached cells and pH. Under the conditions where the repulsion was great, it was visible as a thin transparent zone at the boundary between resin sediment and supernatant. A previously postulated cationic layer around the resin is discussed in terms of the repulsion. When cell concentration in bulk solution increased greatly, free cells again attached to the resin. This was attributed to decreased repulsion and a possible mechanism is discussed.
The effect of copper (CuCl2•2H2O) on growth, heterocyst frequency, acetylene reduction, H2 production and photosynthetic O2 evolution of Nostoc linckia was studied. Whereas copper inhibited growth and other physiological processes, it increased heterocyst frequency and H2 production. We conclude that copper pollution could considerably alter nitrogen dynamics in fresh water systems.
Aspartate and glutamate were formed from glutamine and oxaloacetate with crude enzyme extracts obtained by ammonium sulfate precipitation (35-65% saturation) from the blue-green alga Anabaena cylindrica. In this reaction the 2-amino group of glutamine was transferred to oxaloacetate in the absence of a reluctant. Azaserine, an inhibitor of glutamine -amide transfer, inhibited glutamate formation from glutamine but did not inhibit aspartate formation. Thus, a transamination from glutamine directly to oxaloacetate was indicated. This transamination reaction may be accomplished with glutamine-2-oxoacid transaminase which is found in animal tissues and in yeast.
Microbial films were developed in several packed-bed column reactors and flow channel reactors. Among the nine biofilm reactors investigated, a column reactor packed with thin vinyl strings (1.3mm in diameter), comprising about 10% of the column volume, was best in removing glucose, phenol or TOC from synthetic wastewaters. Ninety percent of glucose (loading of 9.3kg/m3•d) and 75% of TOC (loading of 4.0kg/m3•d) was removed. Toxic wastewater containing phenol was treated successfully with the microbial film reactor when the influent phenol concentration was less than 0.3g/l. More than 90% of phenol was removed from the wastewater containing 0.05g/l of phenol. Glucose removal by microbial films was at the highest rate at an early phase of film development. It decreased considerably at later phases. The half velocity constant for glucose removal was estimated at 0.5-0.7g/l, which was one order of magnitude higher than that reported with suspended cultures of microorganims. This suggests that diffusional resistance of substrate transfer in the attached microbial films was a rate-limiting factor for purification of the polluted water.