Isolation of lactobaciulus

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Como isolar, separar lactobacilo

qué se necesita ?


MRS agar From Wikipedia, the free encyclopedia

Often abbreviated to MRS, this type of bacterial growth medium is so-named by its inventors: de Man, Rogosa and Sharpe. Developed in 1960, this medium was designed to favour the luxuriant growth of Lactobacilli for lab study. It contains sodium acetate, which suppresses the growth of many competing bacteria (although some other Lactobacillales, like Leuconostoc and Pediococcus, may grow). This medium has a clear brown colour.[1] Typical composition

MRS agar typically contains (w/v):[2]

   1.0 % peptone
   0.8 % egg extract
   0.4 % yeast extract
   2.0 % glucose
   0.5 % sodium acetate trihydrate
   0.1 % polysorbate 80 (also known as Tween 80)
   0.2 % dipotassium hydrogen phosphate
   0.2 % triammonium citrate
   0.02 % magnesium sulfate heptahydrate
   0.005 % manganese sulfate tetrahydrate
   1.0 % agar
   pH adjusted to 6.2 at 25°C

The yeast and meat extracts and peptone provide sources of carbon, nitrogen and vitamins for general bacterial growth. The yeast extract also contains vitamins and amino acids specifically required by Lactobacilli. Polysorbate 80 is a surfactant which assists in nutrient uptake by Lactobacilli. Magnesium sulfate and manganese sulfate provide cations used in metabolism.

ox bile/oxall

Principles of the Procedure Oxbile is used as a selective agent for the isolation of Gram-negative microorganisms, inhibiting Gram-positive bacteria.

The major composition of Oxbile is taurocholic and glycocholic acids.

bromocresol purple

Bromocresol purple (BCP) or 5',5"-dibromo-o-cresolsulfophthalein, is a pH indicator. In its sultone form, it has a pKa value of 6.3,[1] and is usually prepared as a 0.04% aqueous solution. Bromocresol purple (pH indicator) below pH 5.2 above pH 6.8 5.2 ⇌ 6.8 Uses

Besides its primary function as an indicator, bromocresol purple is used in medical laboratories to measure albumin, and as an addition to acid stop baths used in photographic processing as an indicator that the bath has reached neutral pH and needs to be replaced.


Strain isolation

The swabs were inoculated onto MRS agar plates (Difco) and incubated at 37°C with partial CO2 tension for 48 h. Growth on MRS was observed for 21 of the 105 analysed samples, and one or more colonies were selected and picked for each of the 21 samples. All colonies were examined by Gram staining and catalase and oxidase tests. A total of 31 strains that were phenotypically consistent with the Lactobacillus genus were chosen and preserved in 25% MRS glycerol at −70°C until DNA extraction.


pep·tone (pĕp′tōn′)n. Any of various water-soluble protein derivatives obtained by partial hydrolysis of a protein by an acid or enzyme during digestion and used in culture media in bacteriology.