Experiments for the examination of culture characteristics of microorganisms

Summary

Culture characteristics of microorganisms refer to the community morphology and growth exhibited by microorganisms cultured on media. The culture characteristics of different microorganisms can generally be examined on slant, liquid and semi-solid media. They can be cultured on slanting media in the form of filamentous, spiny, beaded, sparsely spreading, dendritic or pseudorooted forms.

Operation method

Cultivation Characterization Test

Principle

Growth in liquid medium can be turbid, flocculent, mucus-like, forming a bacterial film, the upper layer is clear and the bottom shows precipitation. Piercing culture in semi-solid medium, can be along the inoculation line to spread around; or only along the line of growth; can also be good growth of the upper layer, or even connected to the bottom of very little growth; or the bottom of the good growth, the upper layer does not even grow. Using the culture characteristics of microorganisms can be used as a reference for their species identification and for recognizing whether a pure culture is contaminated or not. Test the culture characteristics of microorganisms, or other microbiological experiments, the inoculation process must ensure that the other microorganisms are not contaminated, for this reason, in addition to the requirements of the working environment as far as possible to avoid or reduce the contamination of stray bacteria, skilled mastery of a variety of aseptic operation of the inoculation technique is very important.

Materials and Instruments

Bacillus subtilis Escherichia coli Staphylococcus aureus M. albicans Bacillus mycoides Serratia marcescens
Peptone Slant Medium Peptone Liquid Medium Peptone Semi-solid Peptone Medium
Inoculation rings Inoculation needles Sterile pipettes Alcohol lamps

Move

1. Oblique inoculation
(1) On a meat paste peptone slant test tube, write with a marker the name of the organism to be inoculated, the date, and the inoculant.
(2) Light an alcohol or gas lamp.
(3) Hold the strain test tube and the slanted test tube to be inoculated in the left hand with the thumb and forefinger, middle finger and ring finger, and hold the middle finger between the two test tubes so that the slant is up and horizontal. Loosen the test tube stopper with the right hand at the flame side to facilitate pulling out during inoculation.
(4) Sterilize the inoculation ring in the right hand by cauterizing it through a flame, holding the cotton plug (or test-tube cap) by the flame with the edge of the palm of the right hand and the little finger, and the little and ring fingers, respectively, removing it and rapidly cauterizing the mouth of the tube.
(5) Stretch the sterilized inoculation ring into the strain test tube, first contact the ring with the inner wall of the test tube or the medium without bacteria to achieve the purpose of cooling, and then pick a small amount of moss. Exit the inoculation ring into the test tube of the strain and quickly insert it into the slanting test tube to be inoculated, gently draw a straight line with the ring on the slanting surface from the bottom of the test tube to the upper end, do not scratch the medium, and do not make the ring touch the wall of the tube or the mouth of the tube.
(6) Withdraw the inoculation ring from the beveled test tube, then cauterize the mouth of the tube with the flame and cork the test tube at the flame. Gradually approach the inoculation ring to the flame and cauterize it again. If the inoculation ring is stained with more bacteria, the ring should first be roasted dry at the flame, and then cauterized, so as not to contaminate the environment by splashing out the unburned strains, and pay more attention to this point when inoculating pathogenic bacteria.
2. Liquid medium inoculation
To the meat paste peptone liquid medium inoculated with a small amount of bacteria, the procedure is basically the same as the oblique inoculation, the difference is that after picking the inoculation ring of the bacteria into the liquid medium, it should be gently rubbed on the inner wall of the tube at the surface of the liquid, so that the bacteria from the ring off, mixed into the liquid medium, plugged the tube plugs, shake the liquid, so that the bacteria in the liquid is uniformly distributed, or mixing with the test tube oscillator.
When inoculating a large amount of liquid medium or requiring quantitative inoculation, sterile water or liquid medium can be injected into the strain test tube, scrape off the fungal moss with the inoculation ring, and then add the strain suspension by quantitatively sucking it out with a sterile pipette or pouring it directly into the liquid medium. If the strain is a liquid culture, it can be added by quantitative suction with a sterile pipette or poured directly into the liquid culture medium. The whole inoculation process requires aseptic operation.
3. Puncture inoculation
Pick the strain with an inoculating needle (the needle must be straight) and pierce the semi-solid medium vertically from the center of the medium until it is near the bottom of the tube, but do not penetrate, then pull the needle out along the original puncture line, plug the test tube, and cauterize the inoculating needle.
The aseptic manipulation of several of the above inoculation methods, where not described, is operated according to experiment one. The experimenter should practice the aseptic operation of the inoculation technique repeatedly until it is more skillfully mastered.
4. Place the inoculated slant, liquid and semi-solid medium in a 28~30℃ warm box and incubate for 2~3 days before removing and observing the results.

For more product details, please visit Aladdin Scientific website.

https://www.aladdinsci.com/