Multiple Syringe Inoculator for Agar Plates

The design and operation of a manually operated multiple syringe inoculator was described. Either 9 or 21 inoculations of constant volume could be made simultaneously. Up to 100 plates could be inoculated in 15 min with excellent reproducibility. No contact occurred between the inoculating needles and the agar surface. Construction was simple and inexpensive, with minimal maintenance.     

Method for Staining and Preserving Agar Gel Diffusion Plates

An improved method for the preservation of agar gel precipitin lines has been developed.     

Modeling Surface Growth of Escherichia coli on Agar Plates

Surface growth of Escherichia coli cells on a membrane filter placed on a nutrient agar plate under various conditions was studied with a mathematical model. The surface growth of bacterial cells showed a sigmoidal curve with time on a semilogarithmic plot. To describe it, a new logistic model that we presented earlier (H.Fujikawa et al., Food Microbiol. 21:501-509, 2004) was modified. Growth curves at various constant temperatures (10 to 34°C) were successfully described with the modified model (model III). Model III gave better predictions of the rate constant of growth and the lag period than a modified Gompertz model and the Baranyi model. Using the parameter values of model III at the constant temperatures, surface growth at various temperatures was successfully predicted. Surface growth curves at various initial cell numbers were also sigmoidal and converged to the same maximum cell numbers at the stationary phase. Surface growth curves at various nutrient levels were also sigmoidal. The maximum cell number and the rate of growth were lower as the nutrient level decreased. The surface growth curve was the same as that in a liquid, except for the large curvature at the deceleration period. These curves were also well described with model III. The pattern of increase in the ATP content of cells grown on a surface was sigmoidal, similar to that for cell growth. We discovered several characteristics of the surface growth of bacterial cells under various growth conditions and examined the applicability of our model to describe these growth curves.     

Use of Sealed Agar Plates for Bacterial Cultures Under Jungle Conditions

Commercially available sealed blood-agar plates have been demonstrated to retain their usefulness for as long as 3 months under jungle conditions without refrigeration.     

培养基琼脂浓度及抗生素对3种海洋微藻生长的影响

目的:确定用于分离、纯化及保种所用的固体培养基中优化的琼脂浓度和利于微藻生长并抑菌的抗生素浓度。方法:设计固体培养基中的琼脂浓度以及培养液中抗生素的种类和浓度,定时测定培养体系中三种微藻的生物量及细菌菌落随培养时间的变化。结果:利于固体培养基上三种微藻生长的琼脂浓度均为0.6%~0.8%;牟氏角毛藻用200IU/ml的庆大霉素和200IU/ml的青霉素联合作用,球等鞭金藻8701和盐藻分别用300IU/ml和400IU/ml的青霉素时可保证微藻较好生长。结论:不同微藻生长所需的抗生素浓度不同,抗生素对微藻生长的影响不完全取决于抑菌作用,青霉素促进球等鞭金藻8701生长主要是产生促生长因子,庆大霉素抑制生长可能是产生抑制因子。     

Procedure and Analysis of a Useful Method in Determining Mycelial Dry Weights from Agar Plates

The evaluation of growth by dry weight determination of fungus mycelium for agar plates was examined. The data obtained were statistically analyzed. This method was shown to be sufficiently accurate to be used as an investigative tool.     

Punched-Out Agar Petri Plates for Systematic Fixation and Embedding of Multiple Small Tissue Samples

A 5% agar solution is poured into Petri dishes, jelled, and a pattern of cylindrical holes punched out according to the number and size of tissue samples to be processed. These punched-out Petri plates withstand neutral formalin, water, benzene, and paraffin immersion at 60 C; thus providing an adaptable container for processing small tissue samples. Reduced handling of the tissues, minimized risk of loss, and easy identification of samples by means of the map-like arrangement of the holes are among the virtues of such plates. An optimal fixative-volume: tissue-weight ratio can be attained by using wells of varying diameter and depth according to the sample size.     

Effect of Storage of Mueller-Hinton Agar Plates on Zone Sizes for Antimicrobial Testing

The length of time Mueller-Hinton agar plates can be stored at 4 C without affecting the size of zones of inhibition in susceptibility testing by the Bauer-Kirby method was studied. It was found that these plates can be stored for 3 weeks at 4 C without an appreciable affect on zone sizes. Storage of plates in sealed plastic bags did not alter the results significantly. The findings indicate that commercially prepared Mueller-Hinton agar plates, which may be several days old when received at the laboratory, are suitable for use in routine susceptibility tests by the Bauer-Kirby method.     

Rapid Screen for Bacteria Degrading Water-Insoluble, Solid Hydrocarbons on Agar Plates

A rapid procedure was devised for detecting on solid media bacteria able to degrade water-insoluble, solid hydrocarbons such as the polycyclic aromatic hydrocarbons phenanthrene, anthracene, and biphenyl. After Alcaligenes faecalis AFK2 was inoculated on a plate containing mineral salts agar, an ethereal solution of phenanthrene (about 10%, wt/vol) was sprayed on the surface of the plate, and the plate was incubated at 30°C for 2 to 3 days. Colonies showing degradation were surrounded with clear zones on the opaque plate. A similar clear zone also was formed around colonies which had been grown on a succinate-mineral salts agar or nutrient agar, followed by spraying of the ethereal solution of phenanthrene and further incubating for 1 day. Other phenanthrene-assimilating bacteria, including Beijerinckia Bwt and Pseudomonas SPM64, also formed clear zones on phenanthrene-covered agar plates. This method was applicable to detection of bacteria able to assimilate anthracene, naphthalene, and biphenyl.     

Use of Sodium Polyanethol Sulfonate in the Preparation of 5% Sheep Blood Agar Plates

An alternative method to defibrinating sheep blood for use in bacteriological media is described. The new procedure incorporates sodium polyanethol sulfonate in a concentration of 0.05% (vol/vol). In testing 117 bacterial and fungal isolates, no significant differences were found with respect to adequate growth, pigment production, hemolytic reactions, and other physical attributes. Further tests demonstrate that the sodium polyanethol sulfonate in sheep blood agar plates does not cause any aberrations in zone sizes around disks used in antibiotic susceptibility tests. Consequently, the method represents a suitable alternative to the use of defibrinated sheep blood in the preparation of bacteriological media.     

Evaluation of Agar Plates for Direct Enumeration of Campylobacter spp. from Poultry Carcass Rinses

Campy-Cefex, a modification of Campy-Cefex, modified charcoal cefoperazone deoxycholate (mCCDA), Karmali, CAMPY, and Campy-Line agars were evaluated for their efficiency to isolate and enumerate Campylobacter spp. from poultry carcass rinses. Campy-Cefex and its modification produced the best results but were statistically similar to CAMPY, mCCDA, and Karmali.     

A Simple Method for Isolation and Photography of Clostridium Botulinum Colonies from Surface Cultures on Agar Plates

Reflected light gives a very good contrast using blood agar plates in an obliquous position under a stereoscopic microscope. Thus it is possible to isolate pure colonies of Cl. botulinum in the early stage of the growth on blood agar plates.     

Antibiotics Interfere with the Evolution of Plasmid Stability

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Use of Hydrogen Peroxide Treatment and Crystal Violet Agar Plates for Selective Recovery of Bacteriophages from Natural Environments

Hydrogen peroxide inactivated bacteriophages and bacteria at different rates. A concentration of 0.1% hydrogen peroxide reduced the numbers of several bacteria by an average of 94% but caused an average of 25% inactivation in the numbers of bacteriophages tested. Treating natural samples with hydrogen peroxide selectively reduced the indigenous bacterial flora and permitted better visualization of plaques of lawns of Escherichia coli C-3000. In some cases indigenous gram-positive bacteria were relatively resistant to hydrogen peroxide, but their growth could be limited by incorporation of crystal violet into the bottom agar used for plaque assays. The use of hydrogen peroxide treatment and crystal violet-containing plates permitted recovery of more phages from natural samples than did other procedures, such as chloroform pretreatment or the use of selective plating agar such as EC medium.