Pure Cultures Of Microorganisms Research Articles

Zum Einfluß von 2,4-Dioxohexahydro-1,3,5-triazin (DHT) auf Bodenmikroorganismen

Summary After soil application of the antiphytoviral substance 2,4-dioxohexahydro-1,3,5-triazine (DHT) in form of a granulated preparation (30 mg DHT per kg soil) several groups of microorganisms are influenced differently. The amount of soil bacteria was diminished, the quantity of phosphate activating bacteria, of actinomycetes, and of fungi at first increased. 8 weeks after application of DHT the bacteria, actinomycetes, and fungi in plantless soil still were inhibited, in soil with plants the proportions of the microorganisms besides fungi trend to normalize. Pure cultures of microorganisms of 16 or 8 species, respectively, were inhibited by DHT neither in the agar diffusion test (up to 500 μg DHT per hole) nor in aerated liquid cultures (up to 10−2 mol/1 DHT). In unaerated liquid cultures only concentrations of 10−3 to 10−2 mol/1 DHT caused inhibitory effects, in particular with Bacillus subtilis. Stimulating DHT acted especially on Agrobacterium radiobacter.

Effects of pesticides on soil microflora using dalapon as an example.

Effects of the herbicide dalapon on the soil microflora are evaluated. Measurements were made on populations and pure cultures of micro-organisms, dehydrogenase and phosphatase, soil respiration, and nitrogen transformations. At normal concentrations of 2.6 and 26 ppm, dalapon had little effect and is unlikely to harm the soil microflora or soil fertility. At abnormal concentrations of 266 and 2,660 ppm, marked effects occurred on the microflora and its activities. In one soil, 2,660 ppm dalapon significantly increased production of ammonium-nitrogen; nitrification was almost totally inhibited in this soil. The results are discussed in terms of the validity of the tests for detecting effects of pesticides on the soil microflora. Some problems, particularly of data interpretation and evaluation, are high-lighted.

Experimental infections with Staphylococcus aureus, Streptococcus sanguis, Pseudomonas aeruginosa, and Bacteroides fragilis in the jaws of dogs

This investigation was undertaken to determine whether well-characterized microorganisms in pure cultures inoculated into root canals could cause a periapical inflammation and whether these microorganisms could be isolated from pulpectomized but primarily noninfected root canals in other parts of the jaw. The experiments were made on fourteen dogs. In all dogs partial and/or total pulpectomies were performed under aseptic conditions and on the majority of the premolars in each quadrant of the jaw. The pulpectomized roots were inoculated with culture broth alone or culture broth with four different bacterial species ( Staphylococcus aureus, Streptocossus sanguis, Pseudomonas aeruginosa, and Bacteroides fragilis). In each dog only one species was inoculated. Thereafter the teeth were sealed with sterile cotton, fast-setting zinc oxide argard cement, and amalgam fillings. At different time intervals (from 4 up to 120 days) bacteriologic specimens were taken from the noninfected teeth by using sampling fluid (VMG I), charcoaled paper points, and transport medium (VMG III). Bacteriologic samples from the inoculated teeth were taken after 50 and 100 days to test that the inoculated microorganisms were still alive. Cultivation was carried out both aerobically and anaerobically. Radiographs were taken before and during the treatments and at the end of the observation period. A histologic examination was made after the termination of the experiment. The most important findings were the following. The inoculated microorganisms could be isolated from the majority of the primarily noninfected roots after 28 to 120 days, which demonstrated that a transport of microorganisms (anachoresis) had occurred. The roentgenologic examination revealed that radiolucencies could be observed on most roots. On the teeth where no roentgenologic changes could be observed no growth was obtained. The morphologic examination demonstrated a chronic inflammatory reaction on the roots where Pseudomonas aeruginosa and Bacteroides fragilis had been inoculated or could be isolated, while the inflammatory reaction on the roots with Staphylococcus aureus and Streptococcus sanguis was dominated by polymorphonuclear leukocytes.

Succession and activity of microorganisms in stored bagasse

Fresh sugarcane bagasse was fermented under defined conditions and investigated regarding a microbial succession during fermentation, in view of the enzyme activities of microorganisms against the main bagasse components: sucrose, pectin, hemicellulose, cellulose, and lignin. Altogether, 400 pure cultures of microorganisms were obtained from 8 g bagasse during 6.5 days of storage. This flora consists of bacteria (74%), actinomycetes (6%), yeasts (13%), and fungi (7%). The yeasts dominate in early fermentation, followed by bacteria, and then by actinomycetes and fungi. This succession coincides with the enzymic activities of the isolated organisms during fermentation. At first, residual sugar is consumed predominantly by the yeasts. Then the bacteria degrade the pectin, the hemicellulose, and in parts, the cellulose. Later, the actinomycetes and the fungi imperfecti attack the hemicellulose, the cellulose, and, partly, the lignin within the bagasse fiber. These results are corroborated by investigations using bagasse from bulk storage.

Beiträge zum Problem der mikrobiell induzierten Harnstoffumwandlung im Boden: I. Mitt.: Über das Harnstoffverwertungsvermögen von Bodenmikroorganismen

The present publication is the first of a series on the enzymatic urea transformation in soil. With about 2,000 pure cultures of micro-organisms it was possible to prove the very good urea utilization by the soil micro-organisms (bacteria, actinomycetes, and fungi). Above all the fungi showed an excellent utilization of urea, while bacteria and actinomycetes were somewhat poorer. Contrary to this is the urease activity of these organisms, and that is the reason why fungi in soil may be regarded as short-time accumulators for urea nitrogen and must not be suppressed by inhibitors. Die vorliegende Publikation ist eine erste aus einer Publikationsserie über die enzymatische Harnstoffumwandlung im Boden. Es wird an Hand von etwa 2000 Reinkulturen von Mikroorganismen der Nachweis der sehr guten Harnstoffverwertung der Bodenmikroorganismen (Bakterien, Actinomyceten, Pilze) geführt. Pilze verwerteten Harnstoff besonders gut, Bakterien und Actinomyceten etwas schlechter. Umgekehrt verhält sich die Ureaseaktivität der Kulturfiltrate dieser Organismen, weshalb Pilze im Boden als kurzzeitlicher Speicher für Harnstoffstickstoff angesehen werden können und keine Repression durch Inhibition erfahren dürfen.

Measurement of bacterial and fungal contributions to respiration of selected agricultural and forest soils.

A technique using selective inhibitors was used to estimate the relative contributions of bacterial and fungal populations to the respiration of six soils and one litter sample. The ratios of bacterial to fungal respiration in the four agricultural soils, given in percentage of the total microbial activity, ranged from 10/90 to 35/65, with the average ratio being about 30/70. In the forest soils, the ratios were 20/80 and 30/70, and in a beech litter sample, the ratio was 40/60. The fungi clearly dominated in all samples. The ratios were not found to be pH related. The difficulties which had previously limited the use of selective inhibitors for in situ soil ecological investigations, such as insufficient inhibitor specificity, inhibitor inactivation or degradation, and errors of measurement caused by elimination of competitor populations, were either resolved or methodologically avoided in the experiments. Inhibitor selectivity was demonstrated using both mixed and pure cultures of microorganisms from each soil. Through the use of experiments with short incubation periods (6-8 h), problems with population shifts and inhibitor degradation were eliminated.

Microbiological screening of the straight chain fatty acids (c1‐c12) as potential silage additives

AbstractA microbiological screening procedure was used to assess the potential of each of the straight chain members of the series of fatty acids, formic to lauric inclusive, as silage additives. Thirty‐four pure cultures of microorganisms were subjected to serial dilutions of each of the acids in broth buffered at unit pH intervals between 3 and 6 inclusive. All the fatty acids of the series appeared to have potential; the lower members (C1‐C7) prevented the growth of spore‐bearing bacteria and the higher acids had more general antimicrobial effects. A consistent feature of the data obtained was the increase in antimicrobial activity with a decline in pH.

The role of microorganisms in the stabilization of soil aggregates

The maintenance of water-stability of soil aggregates bound by different chemicalbinding agents produced in situ by pure cultures of microorganisms and by an indigenous soil microflora was assessed by wet-sieve analysis. Seven fungi, six streptomycetes, and five bacteria produced binding materials in artificial aggregates of Miami silt loam amended with sucrose. These aggregates generally showed little resistance to biodegradation by a soil population. Comparable aggregates amended with corn stover were more resistant to biodegradation; at least 50 per cent of these aggregates were stable after 64 days. Progressive decreases in the water-stability of these aggregates near the end of 128 day. indicated the depletion of energy sources necessary for the synthesis of aggregating agents. Water-stable aggregates were formed at a faster rate at 30°C than at 15°C, but maximum stability was maintained longer at 15°C than at 30°C. Water-stabilities of aggregates rapidly declined when aggregates bound at 15°C were transferred to 30°C. This indicated biodegradability at 30°C of the binding substances synthesized at 15°C. These data support the hypothesis of Stallings (1953) and endorsed by Harris et al. (1966b) that the status of soil aggregation is determined by the net effect of the continuous synthesis and degradation of binding materials by the microbial population en masse rather than the activity of specific microorganisms. This balance between synthesis and degradation of binding materials is controlled by the prevailing environmental conditions and nutritional factors which affect microbial activity.

DDT metabolized by microorganisms from Lake Michigan.

PERSISTENT chlorinated hydrocarbon insecticides have been used throughout the world for the past two decades, and their residues or metabolites are accumulating in soil and water. There are several reports of microorganisms converting 1,1,1,trichloro-2,2-bis(p-chlorophenyl) ethane (DDT) to 1,1,dichloro-bis(p-chlorophenyl) ethane (TDE)1–7. Other reports indicate that TDE is the principal product of DDT metabolism in aquatic environments8,9. There are, however, no reports of the metabolism of DDT by aquatic microorganisms in pure culture. Here we describe a study of the metabolism of DDT by microorganisms isolated from water and bottom silt of Lake Michigan and related water systems.

The effect of various factors on the extraction of protein from the predominant microorganisms in human dental plaque

A study was made of the effects of pH, temperature, Ca, Mg, ionic strength, osmotic shock, time of exposure to buffer, growth phase and bacterial concentration on the extraction of protein by aqueous solvents from eight representative dental plaque microorganisms in pure culture. Protein extraction was independent of bacterial concentration (0–4 mg total protein/ml), and of ionic strength (0.05–0.64), but was increased by increase in temperature (0 °–60 °C), duration of exposure to solvent and by osmotic shock. Organisms in stationary or early death phase were no more susceptible to protein extraction than were organisms in the logarithmic phase of growth. The minimum extraction was at pH 5.0 and the maximum at pH 12.7. Ca and Mg ions only reduced protein extraction at pH values of 9.0 and above and then only from certain organisms. The results are discussed in relation to the extraction of matrix from dental plaque.

Mikrobiologisen selektion matemaattisista perusteista

For the effective utilization of microorganisms, either in biotechnology or agriculture, it is necessary to increase their original activity considerably. This can be performed by selection because even pure cultures of microorganisms are genetically heterogenous. The determination of the activity in a given strain is carried out in cultivation experiments. The error in the figures obtained decreases with repetition of the process. However, repetition of the determination raises the expenses. This can be compensated by reducing the number of strains included in the repeated experiments. This may involve a loss of profitable strains. The problem thus lies in choosing a selection procedure which minimizes labour and costs. In looking for the most suitable selection procedure mathematical methods may be used. However, in most cases it is difficult to get numerical results, even when assumptions are introduced for the sake of simplification. Computer simulation provides an alternative to solving some of the problems. For other problems it may be possible to find intuitive solutions which may not be the best ones, but are close to them.

Autoradiography as a tool in microbial ecology.

THE importance of micro-organisms as agents of biochemical transformations in natural environments is well established. But micro-organisms are small and thus their environments are also small, so that micro-organisms can be investigated directly in Nature only by the use of the microscope. Although the microscope can be used to see where various organisms are situated in a micro-environment and how organisms are disposed with relation to one another, one cannot, however, study microscopically many of the characteristics of an organism which are of greatest ecological interest: that is to say, nutritional requirements, responses to environmental changes, production of metabolites and growth rate. The usual approach for the study of these latter phenomena has been to isolate micro-organisms in pure culture and attempt to infer from the behaviour of the pure culture the behaviour of the parent organism in Nature. However, it is clear that the behaviour of the pure culture reveals the potentiality of the organism in Nature, but does not show what the organism was actually doing, since the organism has undoubtedly adapted to the cultural conditions used. Further, even if the laboratory conditions precisely mimic the natural conditions, the laboratory environment cannot reproduce the natural environment, since the natural environment contains the additional elements of competition and co-operation with other organisms.

Effect of high CO2 and low O2 tensions on the soil microbiota.

The influence of high pCO2 and low pO2 on the microbiota derived from four tropical soils and on microorganisms in pure culture was investigated. Incubation under atmospheres containing more than 90% CO2 reduced the number of organisms developing on soil dilution plates, but most organisms recovered when the plates were subsequently incubated in air. Inhibition by high CO2 tensions was the result primarily of CO2 concentration and not absence of O2; many organisms developed under 100% N2, and presence of O2 mitigated the inhibitory effects, especially when CO2 concentration was 95% or less. The actinomycete population was most sensitive to high pCO2 and low pO2 and the fungal population least sensitive. Some fungi were capable of developing under 100% N2 and under atmospheres containing as much as 98% CO2; most identified species developed in air after exposure to the various gases. Fusarium oxysporum f. cubense was more tolerant to low O2 and high CO2 tensions than most of the soil mycobiota.

The application of calorimetry to the study of ruminal fermentation in vitro

Techniques evolved for the study of heat production during the metabolism of pure cultures of microorganisms have been adapted for the study of certain aspects of the behaviour of the mixed cultures responsible for fermentation within the rumen. This approach allows whole untreated rumen contents, collected via fistulae, to be studied. The instrument is sensitive to very small changes in the overall evolution of heat, and so is capable of indicating overall changes in metabolic activity. In the samples studied in this series of experiments, the rates of heat and gas (carbon dioxide plus methane) production varied directly with the solids content of the sample. At 24 hr after feeding, the heat produced by ruminal fermentation in the sheep used was calculated to be between 480 and 1360 cal/hr. Ruminal fermentation was not affected by 240 mmoles of volatile fatty acid per litre, but was markedly inhibited by the same level of sodium ion. Lactate ion too appeared to have a specific inhibitory effect. The solid portion of rumen contents was found to possess much greater cellobiose-fermenting activity than did the fluid portion, and lactate accumulated as a transitory intermediate during cellobiose fermentation by whole contents. Small changes in pH had little effect on the course of fermentation in samples collected 16 hr after feeding. These findings and possibilities for the use of calorimetry in the study of complex biological systems are discussed.

INFLUENCE OF MICROBIAL FLORA ON XYLOSE ABSORPTION IN RATS AND MICE.

The absence of a microbial flora produced a twofold increase in the absorption of d-xylose in germfree mice as determined by the everted sac technique. The existence of a similar increase was confirmed in germfree rats by using one in vitro and two in vivo techniques. Monocontamination of germfree mice with pure cultures of microorganisms also produced changes in xylose absorption. Studies on water, Na+, and K+ absorption in germfree mice indicated that the flora produces no significant change in the absorption of Na+ or in the movement of water and K+.

Interrelationships between a yeast and a bacterium when growing together in defined medium.

SINCE the introduction of solid medium, the isolation of micro-organisms in pure culture, formerly a matter of considerable difficulty, has become a relatively easy process. The numerous studies of micro-organisms in pure culture which resulted have enabled the science of microbiology to develop rapidly. In Nature, however, micro-organisms are rarely found in pure culture, and there is a need for investigation of the growth and metabolism of organisms growing in association with each other. Woods1 has recently stressed the need for such research. The present study of a yeast (Saccharomyces cerevisiae) and of a bacterium (a Lactobacillus species) growing separately, and also when growing in association with each other in defined media, was commenced approximately two and a half years ago and is concerned mainly with the nutritional requirements of the micro-organisms. A number of interesting relationships between the organisms when in mixed culture have been observed.

A Study of Hemolytic Streptococci from a Horse Treated with Sulfanilamide after Streptococcal BacteriemiaDeveloped during Immunization

day after treatment was commenced and no hemolytic streptococci were found on direct microscopic examination. The microorganisms in pure culture were present, however, in specimens of blood taken daily thereafter. Since hemolytic streptococci could still be isolated from the blood after 7 days of therapy, the amount of the drug was increased to as much as 900 grains in 1 day, administered in 3 or 4 doses. Treatment was continued with varying amounts and doses until death. The concentration of free sulfanilamide in the blood rose to as high as 28 mg. per hundred cc. and the total sulfanilamide as high as 43 mg. In spite of this, the infection persisted as evidenced by temperatures above normal and the presence of streptococci in the blood. The horse died on the 11th day after treatment was commenced.** Hemolytic streptococci were obtained from the spleen and from a lesion on one of the heart valves.

Microbiology of Frozen Foods: IV. Longevity of Certain Pathogenic Bacteria in Frozen Cherries and in Frozen Cherry Juice

The two papers published here (IV and V) on the microbiology of frozen foods are a part of a rather extensive study of this problem. Because of the length of the complete study it was thought desirable to publish the parts separately. The first of the series contains a review of the literature on the effect of cold temperatures on micro-organisms. The second records studies on about 2,000 cans of frozen fruits and vegetables, in which the longevity of the micro-organisms present was determined. Short studies were also made on tissue changes during freezing and on time of spoilage after freezing. The third was a study of the effect of freezing on pure cultures of micro-organisms suspended in different menstruums. The sixth and last of the series was a study of the longevity of pathogens in ice cream. Those forms which are important in the dairy industries were used, i.e., Mycobacterium tuberculosis (human, bovine and avian types), and paratyphoid and undulant fever strains.

Production of Histamine, Tyramine, Bronchospastic and Arteriospastic Substances in Blood Broth by Pure Cultures of Microorganisms

Production of Histamine, Tyramine, Bronchospastic and Arteriospastic Substances in Blood Broth by Pure Cultures of Microorganisms