Monthly surveys of bat dynamics, temperature, and humidity were performed for the duration of one year in a Romanian cave (Măgurici Cave). Myotis myotis/Myotis blythii, Miniopterus schreibersii, Rhinolophus ferrumequinum, and R. hipposideros were observed. The locations of the bat colonies in the cave are dependent on the temperature, humidity, on the wall structure, and underground ventilation. The air microorganisms present are in direct relation with the location of the bat colonies, showing a pronounced air infestation near the nursing colony during summer.

Biofilms from drains in food processing facilities with a recent history of no detectable Listeria monocytogenes in floor drains were cultured for microorganisms producing antilisterial metabolites. A total of 413 microbial isolates were obtained from 12 drain biofilm samples and were assayed at 15 and 37°C for activities that were bactericidal or inhibitory to L. monocytogenes, by two agar plate assays. Twenty-one of 257 bacterial isolates and 3 of 156 yeast isolates had antilisterial activity. All 24 isolates which produced metabolites inhibitory to L. monocytogenes were assayed for antilisterial activity in coinoculated broth cultures containing tryptic soy broth with yeast extract (TSB-YE). A five-strain mixture of 10(3) CFU of L. monocytogenes/ml and 10(5) CFU of the candidate competitive-exclusion microorganism/ml was combined in TSB-YE and incubated at 37°C for 24 h, 15°C for 14 days, 8°C for 21 days, and 4°C for 28 days. Substantial inhibition of L. monocytogenes growth (4 to 5 log CFU/ml) was observed for nine bacterial isolates at 37°C, two at 15 and 8°C, and three at 4°C. The inhibitory isolates were identified as Enterococcus durans (six isolates), Lactococcus lactis subsp. lactis (two isolates), and Lactobacillus plantarum (one isolate). The anti-L. monocytogenes activity of these isolates was evaluated in biofilms of L. monocytogenes on stainless steel coupons at 37, 15, 8, and 4°C. Results revealed that two isolates (E. durans strain 152 and L. lactis subsp. lactis strain C-1-92) were highly inhibitory to L. monocytogenes (growth inhibition of >5 log10 CFU of L. monocytogenes/cm2). These two bacterial isolates appear to be excellent competitive-exclusion candidates to control L. monocytogenes in biofilms at environmental temperatures of 4 to 37°C.

In microbiological studies in streams, pebble samples have until now been taken out of the water following the conventional method. However, this allows the loss of microorganisms as a result of the removal of overlying water. In the present study, to minimize the loss of microorganisms, we have developed a new sampling method, called the submerged method, for collecting microorganisms living on pebbles in streams. The abundance of microorganisms on natural pebbles and artificial clay tiles, both of which had biofilms developing on their surfaces, was measured using both the conventional and submerged methods and the results from the two methods were compared. The cell densities of bacteria (0.10–14.00 × 10⁸ cells cm⁻²), heterotrophic nanoflagellates (0.36–50.30 × 10⁴ cells cm⁻²), and ciliates (0.071–88.27 × 10² cells cm⁻²) measured by the submerged method tended to be higher than those obtained by the conventional method, although there were only a few cases in which a significant difference existed between microbial abundances determined by the two methods. Also supported by microscopic observation, these results suggest the presence of planktonic and/or weakly attached microorganisms on substrate materials in streams. Significant correlations between the concentration of chlorophyll a and the cell densities of heterotrophic microorganisms and significant correlations among heterotrophic microorganisms suggest the presence of active microbial food webs in streams.

This study investigated microbial detoxification of cyanide in cassava peels and leaves in solid state fermentation. Three microorganisms, Mucor Strictus, Rhizomucor miehei and Saccharomyces cerevisiae were used to inoculate the cassava by-products. The levels of cyanide in the substrates after 4, 8 and 12 days on inoculation with R. miehei were estimated. Cyanide levels in the substrates 7, 14, and 21 days after inoculation with M. strictus and S. cerevisiae were also estimated. The three microorganisms caused a significant (P>0.05) reduction in the cyanide of the leaves and peels. M. strictus and R. miehei caused a 66.67% and 77.13% reduction in cyanide level in leaves respectively. Cyanide in the peels was reduced by 49.52%, 80.68% and 76.69% on inoculation with M. strictus, R. miehei and S. cerevisiae respectively. These changes indicated that R. miehei had the best potential in reducing cyanide of cassava by-products among the three microorganisms used for the study. Factors such as changes in texture in the plant tissue, increase _-glucosidase activity and utilization of the cyanogenic glucosides and their products of fermentation breakdown by the microorganisms possibly explain the observed reduction in cyanide levels by the microorganisms. Three microorganisms used for the study. Factors such as changes in texture in the plant tissue, increase _-glucosidase activity and utilization of the cyanogenic glucosides and their products of fetrmentation breakdown by the microorganisms possibly explain the observed reduction in cyanide levels by the microorganisms. The Journal of Food Technology in Africa Volume 5 Number 2 (April - June 2000), pp. 48-51

Herbicides get into soil and into contact with microorganisms after treatment, which results in their interaction. On the one hand, microorganisms are able to degrade herbicides and utilize them as a source of biogenic elements for their own physiological processes, while on the other hand herbicides have toxic effect on microorganisms, reducing their abundance, activity and consequently diversity of their communities. Various researches have shown that there is no universal pattern for herbicide effect on soil microorganisms. Toxic effects of herbicides are normally most severe immediately after application, when their concentration is soil is the highest. Later on, microorganisms take part in a degradation process, herbicide concentration decreases and so does its toxic effect. Herbicides of the triazine and chloracetanilide chemical groups have exceptionally strong inhibitory effects on soil microflora, decreasing considerably their abundance and activity shortly after the application, as well as over the ensuing period.

A recently reported, miniaturized method can simultaneously enumerate 4 critical indicator microorganisms in 24 h on a single 96-well microtiter plate, and is a convenient monitoring system for ensuring food plant hygiene. However, the utility of this method is limited by the necessity of plates being freshly prepared prior to each use. This study was undertaken to develop a method that would permit these plates to be prepared and stored in a stable form that could be conveniently used later. A microtiter plate filled with media dedicated to enumerating 4 specific classes of bacteria was freeze-dried. A given series was dedicated to enumerating either, total mesophilic bacteria, Gram-negative bacteria, coliform bacteria, or Escherichia coli. Freeze-dried plates were reconstituted simply by adding 100 microliter of sterile water to each well. After adding samples, two-fold serial dilutions were performed, and the plate was incubated for 24 h at 32 degrees C. Growth of 4 indicator microorganisms was detected in each series using metabolic indicators. The numerical estimates that these procedures yielded correlated very closely with numbers gained from conventional spread-plating methods (r2 > 0.90). Additionally, the estimates obtained from liquid media microtiter plates and freeze-dried media plates showed a significantly strong relationship (r2 > 0.92). Analysis of commercial ground beef showed a highly associated relationship (r2 > 0.94) between the liquid four-culture and freeze-dried four-culture plate methods. The greatly enhanced facility of using premanufactured, freeze-dried microtiter plates would make this a most convenient way to perform microbial food quality analysis.

Initial agar plate studies were done to determine the effects of various levels (0 to 2,000 ppm) of potassium sorbate (KS) and sorbic hydroxamic acid (SHA) over a wide pH range (5 to 9) on the growth of microorganisms of spoilage and safety concern in high-moisture, high-pH bakery products. While growth of most microorganisms was inhibited for > 28 days on agar plates containing 1,000 ppm of KS at pH 5 and incubated at 30C, growth of all microorganisms occurred in plates at pH 7 and 9, regardless of the concentration of KS. SHA was equally effective at pH 5, however, it proved to be a more effective inhibitor against most microorganisms at higher pH (9). Subsequent agar plate studies were done with water-ethanol (WE) and mastic oil-ethanol (ME) emitters. While WE emitters failed to control the growth of all microorganisms under investigation, ME emitters controlled the growth of most microorganisms, with the exception of Listeria monocytogenes, for approximately 12 to 28 days on agar plates packaged in high-gas-barrier Cryovac or metallized bags, respectively. Inhibition was not simply due to the levels of ethanol, which ranged from approximately 1.2 to 2.8% v/v, but rather, the mastic volatiles in the package headspace. This study has demonstrated the potential of SHA and ME emitters to control the growth of several microorganisms of spoilage and safety concern in high-moisture, high-pH bakery products. However, the type of packaging material influenced the antimicrobial efficacy of this vapor-phase inhibitor.

Sulforhodamine B (SRB) assay is a rapid, sensitive, and inexpensive method for measuring cell proliferation and chemosensitivity. However, the lactate dehydrogenase (LDH) release assay is generally used to measure cytototoxicity of infectious microorganisms against host cells. In this study, we investigated the possibility of applying the SRB assay to determine cytotoxicity for infectious microorganisms, and compared the results with those obtained by the LDH release assay. We used Vibrio vulnificus as a model of infectious microorganisms. The SRB assay showed that V vulnificus strongly induced cytotoxic activity against human intestinal cells, Caco-2 and INT-407 cells.

Effects of the herbicide nicosulfuron on the activity of soil microorganisms were investigated. Trials were set up on a chernozem soil. Nicosulfuron (preparation Motivell) was applied at 0.5 l/ha, 1 l/ha and 2 l/ha. The abundance of total microflora, actinomycetes, fungi, aminoheterotrophs, aerobic nitrogen fixing bacteria (Azotobacter) and dehydrogenase activity in soil were recorded. Soil samples were collected 3, 7, 14, 30 and 45 days after nicosulfuron treatment for microbiological analyses. The results showed that the intensity of nicosulfuron effect on soil microorganisms depended on treatment rate, length of activity and group of microorganisms. Nicosulfuron had stimulative effect on the number of fungi and actinomycetes. Herbicide treatment reduced the abundance of total microorganisms, aminoheterotrophs and aerobic nitrogen fixing bacteria. Dehydrogenase activity in the examined samples decreased, compared to control.

Focuses primarily on the interactions between plants and microorganisms. Discusses signaling within a symbiosis, the role of microorganisms in growth and development of plants, and the interactions of microbes with genetically modified plants. Also covers microbial population genetics, various aspects of mycorrhizal, and more.