Lab 127 DAY 3

Dichotomous Key

Lara Roelofs

Introduction:

The flow chart below is a dichotomous key used to identify the bacteria according to their morphological and biochemical characteristics

Sentence format Dichotomous Key for Bacteria isolates

1a. Gram Positive Bacteria...............................................................................................................................11

1b. Gram Negative Bacteria............................................................................................................................. 2

2a. Oxidase Positive……………………………………….......................................................................9

2b. Oxidase Negative ........................................................................................................................................3

3a. Citrate utilization positive............................................................................................................................6

3b. Citrate utilization negative ..........................................................................................................................4

4a. Lactose fermentation positive .......................................................................................Escherichia coli

4b. Lactose fermentation negative....................................................................................................................5

5a. Triple Sugar Iron agar (K/A, G 7)................................................................................Proteus vulgaris

5b. Triple Sugar Iron agar (A/?,H2S4 A/A,H2S3).................................................Morganella morganii

6a. H2S Production positive.............................................................................................................................8

6b. H2S Production negative............................................................................................................................7

7a. Methyl Red production positive...................................................................... Klebsiella pneumoniae

7b. Methyl Red production negative....................................................................Enterobacter aerogenes

8a. Lactose fermentation positive .......................................................................Citrobacter freundii

8b. Lactose fermentation negative .............................................................................Salmonella pullorum

9a. Sucrose Fermentation positive…………......................................................Aeromonas hydrophila

9b. Sucrose Fermentation negative................................................................................................................10

10a. Nitrate Reduction positive.........................................................................Pseudomonas aeruginosa

10bNitrate Reduction negative.................................................................................Alcaligenes faecalis

11a. Nitrate Reduction positive.......................................................................................................................14

11b. Nitrate Reduction negative....................................................................................................................12

12a. Motility present...................................................................................................................Listeria grayi

12b. Motility absent..........................................................................................................................................13

13a. Methyl Red present.................................................................................Corynebacterium xerosis

13b. Methyl Red absent...............................................................................Mycobacterium smegmatis

14a. Starch Hydrolysis positive.......................................................................................................................16

14b. Starch Hydrolysis negative....................................................................................................................15

15a. Casein Hydrolysis positive..................................................................................Bacillus laterosporus

15b. Casein Hydrolysis negative...............................................................Corynebacterium diphtheriae

16a. Methyl Red present..............................................................................................Bacillus megaterium

16bMethyl Red absent...........................................................................................................Bacillus subtilis