Phthalic acid esters (PAEs), due to their teratogenic and mutagenic properties, threaten to disturb the ecological balance. Di-octyl phthalate (DOP) and di-2-ethylhexyl phthalate (DEHP) esters are present in the environment as micropollutants, originating from industrial usages in plastics. Because of the probability that PAEs also occur naturally, it was expected that soil and water microorganisms would utilize PAEs during the performance of their normal role in the cyclization of carbon in nature. Since this assumption is not sufficiently supported in the literature, a study was conducted to determine whether soil microorganisms utilize DOP and DEHP. A loam soil was incubated at 4, 10, 22 to 25 and 32C with DOP, DEHP and two other PAEs. Soil respiration rates were measured after 14 weeks, either with or without fresh additions of the PAEs. Increased rates of respiration, indicating microbial utilization of all the PAEs, were recorded. However, the results indicated that DOP and DEHP are used only marginally at 4 and 10C.

A newly developing source of hydrocolloids for use in foods is based on the ability of nonpathogenic microorganisms to produce polysaccharides. This paper reviews some of the basic research and associated industrial development of extracellular microbial polysaccharides [e.g. dextran, xanthan] for practical uses in foods.

A mathematical model based on Michaelis-Menten kinetics for oxidation of ammonium to nitrate during downward flow in a column of soil mixed with sand has been tested. First the column was perfused with nitrite to stimulate the growth of nitrite oxidizing microorganisms in order to decrease the concentration of nitrite at any time in the column during subsequent perfusion with ammonium. The nitrite oxidizers multiplied in a quasilogistic fashion to nearly maximal numbers, exceeding ammonium oxidizers by at least a factor of 10². After a population density of 10³/cm³ was reached for NO₂⁻ oxidizers, the column was perfused with ammonium solution; in a steady state the ammonium concentration decreased with depth (proportional to time of flow) in accord with Michaelis-Menten kinetics. The rate constants for oxidation of NH₄⁺ were proportional to the numbers of ammonium oxidizing microorganisms extant at any given time of observation; these numbers increased exponentially at first but leveled off after about 3 weeks of continuous perfusion of the column. As expected, the decline of ammonium concentration with depth during solution flow just equalled the appearance of nitrate with very low concentrations of nitrite in the steady state. From the data the normalized rate constant is 4.5 × 10⁻³ ppm cm³/hour per microbe at room temperature, about five times greater than the corresponding figure for nitrite oxidation.

Land application of animal residues containing large numbers of viable pathogenic microorganisms is not an acceptable practice. Information is needed upon which to base storage guidelines to ensure extensive pathogen dieoff. Salmonellae inoculated into samples of poultry excreta declined to very low numbers or disappeared within a month, as judged by a specific most-probable-number procedure. The decline was usually preceded by a period of growth, however. Overall reductions of 99% were achieved, on the average, in 19 days when incubation was at 9 to 12C, in 11 days at 18 to 20C, and in 3 days at 30C. Although drying excreta at room temperature killed 99.5% of the inoculated cells, survivors persisted for relatively long periods of time. Storage of undried excreta is an effective means of killing salmonellae.

Suspensions of axenically grown algae underwent aerobic decomposition in a solution free of nitrogen, phosphorus, and organic carbon. The rate and extent of mineralization of algal cell carbon and nitrogen and the solubilization of algal cell phosphorus varied appreciably among the test organisms. Chlamydomonas oblonga underwent rapid decomposition; Chlorella sp. lost carbon, nitrogen, and phosphorus slowly; and Ankistrodesmus falcatus and Astemcoccus superbus lost their carbon, nitrogen, and phosphorus at intermediate rates. Microorganisms from sewage markedly influenced the rate of liberation of some of the elements contained in A. falcatus and A. superbus but had little or no effect on the mineralization of carbon and nitrogen or on the release of phosphorus from cells of C. oblonga and Chlorella sp. Cells from 14-day cultures of C. oblonga and A. falcatus were more quickly decomposed than cells from 28-day cultures.

Studies were conducted to evaluate influences of antecedent soil moisture suction on saturated hydraulic conductivities of soils. These studies revealed that saturated hydraulic conductivity of a soil is a dynamic property which is markedly influenced by antecedent soil moisture suction. Antecedent soil moisture of ≤ 0.33 bar suction, such as is often practiced with trickle irrigation, caused marked reduction in the ability of soil to conduct water. Gases produced by microorganisms at low suction, their subsequent entrapment, and their influence on soil macrovoids are largely responsible for reduction in ability of soil to conduct water. Reduction of effective soil macrovoids by microbial growth, flowing water, and/or soil moisture suction can also reduce soil permeability. These findings indicate that soil moisture suction and management such as trickle irrigation can influence the ability of soil to conduct water.

Mirex (dodecachlorooctahydro-1,3,4-metheno-2H-cyclobuta [cd] pentalene) in corncob grit bait and in spray form was applied to oak (Quercus alba L.) and dogwood (Cornus florida L.) leaf litter in mesh bags, on 20 5m by 5m plots. Macroarthropod fauna was monitored by capture in pitfall traps, and microarthropod populations were extracted from litter bags and counted. Ant presence on plots was tested by use of blank bait and molasses. Mirex in bait and spray form, and at the two levels applied, caused a significant acceleration in litter decomposition. The two leaf species as expected showed significantly different decomposition rates, and the slope of the ground surface on which the bags were placed was found to influence the decomposition process. The two leaf species differed in the amount of decomposition shown with mirex treatment, dogwood being more affected than oak. Ants were essentially removed from bait and concentrated spray plots up to 79 days, but ants had returned to all plots by the 334th day after treatment. The low spray treatment had no effect on the ant populations. Macroarthropods captured were spiders (Araneida), beetles (Coleoptera), millipedes (Orthomorpha gracilis), scorpions (Scorpionida), and centipedes (Scutigerella immaculata). Little difference was observed with treatment except with centipedes whose numbers appeared to decrease on the bait and concentrated spray plots. Microarthropod populations showed significant differences with treatment, at different times during the experiment, but no overall pattern could be detected that might explain the leaf decomposition acceleration noted with all treatments. Since microarthropod, macroarthropods and microflora are known to be involved in the decomposition, and since neither the microarthropods nor the macroarthropods could account for the change in decomposition then by extrapolation the groups most probably affected by the mirex would be the bacteria and fungi. These organisms were not monitored. It is speculated that mirex could have accelerated decomposition through its ability to induce mixed-function oxidase systems in the microorganisms. These enzymes are responsible for the breakdown of numerous xenobiotics or foreign compounds. If synthesis of more of these enzymes by fungi and/or bacteria allowed faster metabolism of the plant inhibitor, tannic acid, then decomposition could have received an early boost due to the growth of microorganisms usually limited by tannic acid.

Scanning-electron micrographs were made of Dactylis glomerata L. leaf tissue following digestion in rumen fluid to observe differential digestion of various cell types. Fresh leaf blade sections were subjected to the activity of rumen fluid at 39C obtained from a rumen-fistulated Black Angus steer. Digestion by rumen microorganisms allowed the cuticle to float free as the mesophyll was digested. Close examination revealed that the stomatal guard cells were slow to digest and that they remained attached to the interior surface of the cuticle. The lack of significant microorganismal entrance into fresh leaf tissue, except through cut edges, may be explained by the combined resistance of the cuticle and stomatal guard cells to digestion. We propose that the cellulose of guard cell walls of Dactylis glomerata L. is infused with either a cutin-like compound or with silica. Possibly a combination of cutin and silica provides guard cells with resistance to digestion by rumen fluid organisms. Additionally, electron micrographs are presented that vividly display the shape and orientation of the guard cells from a new perspective.