Digestive tracts from two catfishes (labeled as samples 1 and 2)
were sterilely dissected and washed. The fish intestines were cut,
weighed and homogenized in Man Rogossa Sharp (MRS) agar and
vortexed. These were serially diluted (from 10-1 to 10-6 for two
samples, respectively) and were pour plated on MRS agar. The
plates were incubated anaerobically, at 30°C for 48 h. Single
colonies developed were picked up for morphological, lactose
utilization, gram reaction, catalase ad antimicrobial test, and further,
genomic extraction for rRNA sequencing.
In lactose utilization test, the selected colonies were then
streaked onto nutrient agar NA with the addition of lactose
containing 0.005 g/L bromo-cresol purple, as a pH indicator dye.
The plates were incubated at 30°C for 24 h. Isolates that were able
to utilize lactose and produce acid were differentiated by the
change of media color from violet to yellow. Catalase activity was
tested by adding a drop of 30% hydrogen peroxide solution onto the
cell smears. Positive reaction would be seen as bubbles or froths
generated from the colonies, indicating a rapid production of
oxygen gas. Only isolates that showed negative reaction were
subjected to further identification test.
The antagonistic activity of the isolated LAB against Salmonella
typhimurium and Escherichia coli were determined by using agar
disc diffusion. LAB isolate was propagated in MRS broth medium
and incubated anaerobically at 30°C for 48 h. Cell propagated in
MRS broth was pipette onto 5 mm diameter filter paper disc
(diameter of 5 mm, Whatman No.1) and dried for 10 min. About 500
μl of indicator organism, (either S. typhimurium or E. coli) was
spread on the plates. The test was performed in triplicates. Then,
the plates were incubated at 37°C for 24 h and the zone of
inhibitions formed surrounding the disc was observed.
Following overnight incubation at 30°C in 10 ml MRS broth,
genomic extraction was carried out using DNeasy Blood and Tissue
Digestive tracts from two catfishes (labeled as samples 1 and 2)were sterilely dissected and washed. The fish intestines were cut,weighed and homogenized in Man Rogossa Sharp (MRS) agar andvortexed. These were serially diluted (from 10-1 to 10-6 for twosamples, respectively) and were pour plated on MRS agar. Theplates were incubated anaerobically, at 30°C for 48 h. Singlecolonies developed were picked up for morphological, lactoseutilization, gram reaction, catalase ad antimicrobial test, and further,genomic extraction for rRNA sequencing.In lactose utilization test, the selected colonies were thenstreaked onto nutrient agar NA with the addition of lactosecontaining 0.005 g/L bromo-cresol purple, as a pH indicator dye.The plates were incubated at 30°C for 24 h. Isolates that were ableto utilize lactose and produce acid were differentiated by thechange of media color from violet to yellow. Catalase activity wastested by adding a drop of 30% hydrogen peroxide solution onto thecell smears. Positive reaction would be seen as bubbles or frothsgenerated from the colonies, indicating a rapid production ofoxygen gas. Only isolates that showed negative reaction weresubjected to further identification test.The antagonistic activity of the isolated LAB against Salmonellatyphimurium and Escherichia coli were determined by using agardisc diffusion. LAB isolate was propagated in MRS broth mediumand incubated anaerobically at 30°C for 48 h. Cell propagated inMRS broth was pipette onto 5 mm diameter filter paper disc(diameter of 5 mm, Whatman No.1) and dried for 10 min. About 500μl of indicator organism, (either S. typhimurium or E. coli) wasspread on the plates. The test was performed in triplicates. Then,the plates were incubated at 37°C for 24 h and the zone ofinhibitions formed surrounding the disc was observed.Following overnight incubation at 30°C in 10 ml MRS broth,genomic extraction was carried out using DNeasy Blood and Tissue
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