Though Staphylococcus aureus can grow in foods within a broad range of environmental conditions, production of enterotoxins occurs within a much narrower range. In situations that permit growth of S. aureus, oxygen tension and associative growth of other microorganisms affect enterotoxin production more adversely than other factors such as temperature, pH, and water activity. Minimal amounts of enterotoxins or none may be produced in raw, semiprocessed, or fermented foods when there is competitive growth of other microorganisms unless such growth is retarded by bacteriophages, antibiotics, organic acids, and processing conditions such as curing and heating.

Eighteen of 19 strains of Saccharomycopsis fibuligera and one of two strains of S. capsularis produced mixtures of C(14)-C(18) 2-D-hydroxy acids in liquid culture medium. The mixture of these acids showed antimicrobial activity against Vibrio tyrogenus but not against the other microorganisms tested. Candida lactosa, a recently described species, was shown to be an isolates of S. fibuligera.

Leaves of ‘Kentucky 31’ tall fescue (Festuca arundinacea Schreb.) and ‘Coastal’ bermudagrass (Cynodon doctylon (L) Pers.) were studied to relate microanatomical differences to differences in degradation. Leaf sections of each grass were incubated with rumen microorganisms for various tunes and examined using the scanning electron microscope. Data reveal that tall fescue is degraded more rapidly and extensively than Coastal bermudagrass. These differences agree with in vitro dry matter disappearance investigations conducted on leaf tissue of each grass. Portions of the lignified structures in tall fescue appear to be removed after a 72-hour incubation, whereas all lignified tissues in Coastal bermudagrass are completely undegraded at this time. Data indicate that the amounts of particular tissues in grass leaves affect the rate of tissue degradation.

Contrary to reports in the literature, no correlation was found between the peroxidase activity of five soils or the numbers of peroxidase-producing microorganisms and the abilities of the soils to condense 3,4-dichloroaniline (DCA) derived from the hydrolysis of N-(3,4-dichlorophenyl) propionamide (propanil) to 3,3′,4,4′-tetrachloroazobenzene (TCAB). Amending the soils with an energy source increased the production of peroxidase extractable from the soil but decreased the amount of TCAB formed. It has been reported that a peroxidase-producing fungus isolated from soil was capable of converting DCA to TCAB. However, peroxidase isolated directly from a soil of this study was incapable of converting DCA to TCAB. Apparently not all soil peroxidases catalyze the conversion.

Carbon dioxide evolution from the floor of an oak-hickory (Quercus sp.) (Carya sp.) forest was studied. The influence of soil temperature, soil moisture, and position on a west-facing slope was evaluated on a seasonal basis. Highest evolution rates were observed during the summer and declined in the order of fall, spring, and winter. Maximum summer rates were 1.20 g/m² per hour while maximum winter rates were 0.18 g/m² per hour. Temperature was found to have its greatest limiting effect during the winter and spring while moisture was most limiting during the fall. Release of CO₂ at the lower slope position was 20% greater on a mean annual basis than at the middle and upper slope positions. Most of the CO₂ evolved from the forest floor is considered to be contributed by root respiration and associated microorganisms.

The kinetics for first-order multisequence reactions are derived for microbial fractionation of ¹⁴N and ¹⁵N isotopes. The isotope effect accounts for unreacted substrate becoming progressively enriched in the heavier isotope due to preferential utilization of the lighter isotope by microorganisms. Consequently, during denitrification nitrate becomes enriched in ¹⁵N as its concentration diminishes. This inverse proportional relationship is expressed as a hyperbolic function, y = ax⁻ᵇ. Similar curves are derived for nitrate originating from ammonification and/or nitrification. Regression coefficients for a straight line approximation are better than −0.98, but not as good as the actual coefficients for the derived hyperbolic equations. A negative regression “line” for nitrate occurs for all denitrification reactions during isotope discrimination. Nitrate originating from caesin, ammonium, and nitrate are respectively less enriched in ¹⁵N for equal nitrate concentration due to ammonium and nitrate being initially enriched in ¹⁴N during ammonification and nitrification, respectively.

A survey of literature relating to septic tanks and the movement of micro-organisms through soil was made. The septic tank still appears to be the most satisfactory method of treating household wastes. Little experimental evidence is available concerning the movement of microorganisms through soil, but work which has been done indicates that soils vary greatly in their filtering ability. Furthermore soils appear to change in capacity to retain micro-organisms which subsequently die at different rates depending on the nature of the soil. The travel of viruses through ~oil has received negligible attention. Investigations undertaken at two sites in the Tai Tapu Area, near Christchurch, indicated that pollution of the soil by faecal organisms can take place from septic tanks and can extend over quite a wide area. The bacteria may remain viable in the soil for some months, both near the surface and at depth. From samples obtained by drilling holes in the soil it was found that bacteria could apparently move laterally through the soil at 2.0 to 3.0 m depth for considerable distances. Two main conclusions can be drawn from this work. First, soil can become contaminated by septic tank effluent over a wide area. Second, once the soil is contaminated the micro-organisms can persist for long periods.

The blue-green algae, for a long time a disregarded group of microorganisms, are now a fashionable subject for research. The possible reasons for this are various. One may be that current speculations about the origin and early evolution of life have reminded biologists that this is a group of undoubted antiquity. It has biochemical characteristics, on the one hand, which may be related to an existence on the primitive Earth and, on the other hand, it shows possible links with the green plants which are dominant today. Another reason may be that the electron microscope has revealed features of fine structure which confirm the long suspected kinship of these organisms with the bacteria. Mounting evidence that blue-green algae play an important, if unobtrusive, part in maintaining soil fertility and the often all too obvious fact that they are a nuisance in freshwater have also made their study of some economic importance. This upsurge of interest has been exhilarating, as ways of solving apparently insoluble problems have presented themselves, facts have fallen into place, and intriguing new questions have arisen. Nevertheless there is an increasing mass of specialist literature and now is the time to attempt the assembly of a unified picture of blue-green algae as living organisms. The authors hope that the result will be of use to students and research workers in various branches of botany, microbiology, and biochemistry.

The acetylene reduction assay has been used extensively to detect and measure nitrogenase activity of free-living microorganisms, excised legume and non-legume nodules, and root systems, soil cores, and entire nodulated legume plants removed from their soil medium. This investigation was undertaken to determine whether or not the acetylene reduction assay can be used to measure nitrogenase activity of cultures of nodulated soybean (Glycine max.) plants in situ and to compare the nitrogenase activity of these cultures with the nitrogenase activity of detached nodules and excised root systems from comparable cultures. Entire cultures grown in Perlite or in soll were placed in polyethylene containers, covered with Plexiglas lids, exposed to acetylene, and assayed for ethylene production. Time course experiments showed that rates of acetylene reduction of plants growing in Perlite and in soil were linear for at least 90 min following an initial lag period of 15 min. Saturation of nitrogenase in intact cultures was obtained at a pC₂H₂ of 0.1 atm. The apparent Km for nitrogenase was 0.05 atm. For convemence, assays in the large containers were conducted at a pC₂H₂ of 0.025 atm. The Michaelis-Menten equation was used to calculate rates of acetylene reduction at saturating levels of acetylene. The correlation coefficient between rates of acetylene reduction and nodule fresh weight was 0.99 for plants of the same age and 0.79 for plants of different ages. Acetylene reduction rates of either intact nodulated plants in Perlite or nodulated root systems removed from Perlite were significantly greater than acetylene reduction rates of detached nodules from comparable cultures. Relatively little diurnal variation was observed in nitrogenase activity of potted plants grown under controlled environmental conditions. The method is useful for the assessment of nitrogenase activity of legume cultures in a porous medium under standardized conditions, but its application to legumes in soil proved to be complicated by the water content of the soil which influences rates of gas diffusion within the culture medium.