Flat-panel bacterios counting

experiment 31 flat-panel bacterios counting method 1, the purpose requires to learn the basic principles and methods of flat-panel bacterios counting.2. Basic principles Flat-panel bacterios counting is based on the
microbials
on the solid
culture
base formed by a single-celled phenomenon, that is, a single-celled formation of a single-cell, that is, a single-cell. Counting, the sample to be tested for a series of dilution, and then take a certain amount of diluted bacteria inoculated into the petri dish, so that it is evenly distributed in the flat dish
medium
, after culture, by a single cell growth and reproduction to form a bacterios,
stattation
number of places, you can calculate the number of bacteria in the sample.advantage of this counting method is that the number of live bacteria in the sample can be measured. This method is often used for the detection of certain finished products (e.g. insecticides), biological products and food, water pollution, etc. However, the procedure of flat-panel bacterios counting is more complicated, and the measurement value is often affected by various factors., equipment E. coli suspension, beef paste proteinculture base, 1 ml sterile straw, sterile flat dish, containing 4. 5 ml sterile water test tube, test tube rack and marker pen, etc., the operation step 1. Number:9 sets of sterile flat dishes, marked with a marker pen 10
-4
, 10
-5
, 10
-6
each 3 sets. Take another six with 4. 5 ml of sterile water test tube, arranged on the test tube rack, in order marked 10
-1
, 10
-2
, 10
-3
, 10
-4
, 10
-5
, 10
-6
.2． Diluted0. with 1 ml sterile straw. 5 ml E. coli suspension into a test tube of 10
-1
, pay attention to the tip of the straw do not touch the liquid surface, so as not to blow out, the liquid in the tube overflow. Then still use this straw to blow the pipe suspension back and forth three times, when sucking into the bottom of the tube, blowing away from the water surface, so that it mixes evenly. Take another straw from 10
-1
test tube 0. 5ml into a
-2
tube and blow three times,...... The rest are, by analogy. The entire dilution process is shown in Figure VIII.-3.3． Sampling3 1 ml sterile straws were used to accurately absorb 10
-4
, 10
-5
, 10
-6
dilution 0. 2 ml, put the numbers in a numbered sterile petri dish.4． Inverted platein the above-mentioned Petri dish with different dilution bacteria liquid, poured into the dissolved and cooled to about 45 degrees C of the paste protein
agaride
medium about 10-15 ml, placed horizontal position, quickly spin and mix well, to be solidified, poured into a 37 degrees C greenhouse culture.5． Counting After 24 hours of culture, remove the petri dish, calculate the average number of bacterios on the same dilution of three flat dishes, and calculate according to the following formula:total live bacteria per milliliter - the same dilution three times repeated the average of the bacteria× dilution multiplication×5 generally choose each plate with 30-300 bacteria per milliliter of dilution to calculate the most appropriate bacteria per milliliter. The number of three duplicate bacteria of the same dilution degree cannot vary widely. The total number of live bacteria per milliliter of bacteria calculated from 10
-4
, 10
-5
, 10
-6
can not vary widely, such as a large difference, indicating that the test is not accurate.the flat plate bacterios counting method, the dilution of the selected reverse plate is very important, generally with the second dilution of the three dilutions of the flat plate appeared in the average number of vertemics in about 50 is the best.addition to the above, the operation of the flat plate bacteria counting method can also be carried out by coating the plate. The operation of the two is basically the same, the difference is that the coating plate method is first the beef paste protein agar medium dissolved and then poured flat plate, to be solidified after the number, and baked in a greenhouse at 37 degrees C for about 30 minutes, so that it
coisting
, and then with a sterile straw to absorb 0. 2 ml of bacterial liquid pair inoculated on different dilution number of petri dishes on the medium, and then with sterile glass scraper on the plate evenly coated, flat on the
test bench
20-30 minutes, so that the liquid penetrates into the medium, and then poured into a greenhouse at 37 degrees C culture., the experimental report1. Resultscount results are filled in the table below.
2． Question:(1) why does the dissolved culture base have to be cooled to about 45 degrees C to reverse the plate?(2) What are the keys to accurately counting flat bacterios? Why?(3) the same bacteria liquid with blood cell counting board and flat plate bacteria counting at the same time, the result is the same? Why?(4) try to compare the advantages and disadvantages of flat-panel

and microscope direct counting under the microscope.