How to Make a Dichotomous Key From a Table of Bacterial Characteristics (for use in running the minimum number of tests in identifying an unknown bacterium)

Table of Characteristics for Eight Bacteria Organism Characteristics Alcaligenes faecalis Gram negative bacillus, acid-fast negative, ferments galactose, catalase positive, motile, alkaline with litmus milk, not hemolytic, H2S negative Citrobacter freundii Gram negative bacillus; acid-fast negative, does not ferment galactose, catalase positive, non-motile, acid produced in litmus milk, not hemolytic, H2S negative Pseudomonas fluorescens Gram negative bacillus, acid-fast negative, does not ferment galactose, catalase positive, non-motile, alkaline in litmus milk, hemolytic, H2S negative Streptococcus pneumoniae Gram positive oval coccus found as streptococci, acid-fast negative, galactose fermentation negative, catalase negative, non-motile, acid in litmus milk, hemolytic, H2S negative Mycobacterium smegmatis Gram positive club-shaped bacilli, acid-fast positive, galactose fermentation negative, catalase-negative,, non-motile, alkaline in litmus milk, catalase positive, not hemolytic, H2S negative Mycobacterium leprae Gram positive club-shaped bacilli, acid-fast positive, galactose fermentation negative, catalase-positive, non-motile, alkaline in litmus milk not hemolytic, H2S negative Corynebacterium xerosis Gram positive club-shaped bacilli, acid-fast negative, galactose fermentation positive, non-motile, acid from litmus milk, catalase positive, not hemolytic, H2S negative Aeromonas hydrophila Gram negative bacilli, acid-fast negative, ferments galactose, catalase positive, motile, acid from litmus milk, not hemolytic, H2S positive

Dichotomous Key to Identifying Eight Bacteria Alcaligenes faecalis Mycobacterium smegmatis Citrobacter freundii Mycobacterium leprae Pseudomonas fluorescens Corynebacterium xerosis Streptococcus pneumoniae Aeromonas hydrophila

Table of Characteristics for Eight Bacteria Organism Characteristics Alcaligenes faecalis Gram negative bacillus, acid-fast negative, ferments galactose, catalase positive, motile, alkaline with litmus milk, not hemolytic, H2S negative Citrobacter freundii Gram negative bacillus; acid-fast negative, does not ferment galactose, catalase positive, non-motile, acid produced in litmus milk, not hemolytic, H2S negative Pseudomonas fluorescens Gram negative bacillus, acid-fast negative, does not ferment galactose, catalase positive, non-motile, alkaline in litmus milk, hemolytic, H2S negative Streptococcus pneumoniae Gram positive oval coccus found as streptococci, acid-fast negative, galactose fermentation negative, catalase negative, non-motile, acid in litmus milk, hemolytic, H2S negative Mycobacterium smegmatis Gram positive club-shaped bacilli, acid-fast positive, galactose fermentation negative, catalase-negative,, non-motile, alkaline in litmus milk, catalase positive, not hemolytic, H2S negative Mycobacterium leprae Gram positive club-shaped bacilli, acid-fast positive, galactose fermentation negative, catalase-positive, non-motile, alkaline in litmus milk not hemolytic, H2S negative Corynebacterium xerosis Gram positive club-shaped bacilli, acid-fast negative, galactose fermentation positive, non-motile, acid from litmus milk, catalase positive, not hemolytic, H2S negative Aeromonas hydrophila Gram negative bacilli, acid-fast negative, ferments galactose, catalase positive, motile, acid from litmus milk, not hemolytic, H2S positive

Table of Characteristics for Eight Bacteria Organism Characteristics Alcaligenes faecalis Gram negative bacillus, acid-fast negative, ferments galactose, catalase positive, motile, alkaline with litmus milk, not hemolytic, H2S negative Citrobacter freundii Gram negative bacillus; acid-fast negative, does not ferment galactose, catalase positive, non-motile, acid produced in litmus milk, not hemolytic, H2S negative Pseudomonas fluorescens Gram negative bacillus, acid-fast negative, does not ferment galactose, catalase positive, non-motile, alkaline in litmus milk, hemolytic, H2S negative Streptococcus pneumoniae Gram positive oval coccus found as streptococci, acid-fast negative, galactose fermentation negative, catalase negative, non-motile, acid in litmus milk, hemolytic, H2S negative Mycobacterium smegmatis Gram positive club-shaped bacilli, acid-fast positive, galactose fermentation negative, catalase-negative,, non-motile, alkaline in litmus milk, catalase positive, not hemolytic, H2S negative Mycobacterium leprae Gram positive club-shaped bacilli, acid-fast positive, galactose fermentation negative, catalase-positive, non-motile, alkaline in litmus milk not hemolytic, H2S negative Corynebacterium xerosis Gram positive club-shaped bacilli, acid-fast negative, galactose fermentation positive, non-motile, acid from litmus milk, catalase positive, not hemolytic, H2S negative Aeromonas hydrophila Gram negative bacilli, acid-fast negative, ferments galactose, catalase positive, motile, acid from litmus milk, not hemolytic, H2S positive

Dichotomous Key to Identifying Eight Bacteria Alcaligenes faecalis Mycobacterium smegmatis Citrobacter freundii Mycobacterium leprae Pseudomonas fluorescens Corynebacterium xerosis Streptococcus pneumoniae Aeromonas hydrophila Gram stain negative positive Alcaligenes faecalis Mycobacterium smegmatis Citrobacter freundii Mycobacterium leprae Pseudomonas fluorescens Corynebacterium xerosis Aeromonas hydrophila Streptococcus pneumoniae

Table of Characteristics for Eight Bacteria Organism Characteristics Alcaligenes faecalis Gram negative bacillus, acid-fast negative, ferments galactose, catalase positive, motile, alkaline with litmus milk, not hemolytic, H2S negative Citrobacter freundii Gram negative bacillus; acid-fast negative, does not ferment galactose, catalase positive, non-motile, acid produced in litmus milk, not hemolytic, H2S negative Pseudomonas fluorescens Gram negative bacillus, acid-fast negative, does not ferment galactose, catalase positive, non-motile, alkaline in litmus milk, hemolytic, H2S negative Streptococcus pneumoniae Gram positive oval coccus found as streptococci, acid-fast negative, galactose fermentation negative, catalase negative, non-motile, acid in litmus milk, hemolytic, H2S negative Mycobacterium smegmatis Gram positive club-shaped bacilli, acid-fast positive, galactose fermentation negative, catalase-negative,, non-motile, alkaline in litmus milk, catalase positive, not hemolytic, H2S negative Mycobacterium leprae Gram positive club-shaped bacilli, acid-fast positive, galactose fermentation negative, catalase-positive, non-motile, alkaline in litmus milk not hemolytic, H2S negative Corynebacterium xerosis Gram positive club-shaped bacilli, acid-fast negative, galactose fermentation positive, non-motile, acid from litmus milk, catalase positive, not hemolytic, H2S negative Aeromonas hydrophila Gram negative bacilli, acid-fast negative, ferments galactose, catalase positive, motile, acid from litmus milk, not hemolytic, H2S positive

Dichotomous Key to Identifying Eight Bacteria Alcaligenes faecalis Mycobacterium smegmatis Citrobacter freundii Mycobacterium leprae Pseudomonas fluorescens Corynebacterium xerosis Streptococcus pneumoniae Aeromonas hydrophila Gram stain negative positive Alcaligenes faecalis Mycobacterium smegmatis Citrobacter freundii Mycobacterium leprae Pseudomonas fluorescens Corynebacterium xerosis Aeromonas hydrophila Streptococcus pneumoniae Galactose fermentation positive negative Alcaligenes faecalis Citrobacter freundii Aeromonas hydrophila Pseudomonas fluorescens

Table of Characteristics for Eight Bacteria Organism Characteristics Alcaligenes faecalis Gram negative bacillus, acid-fast negative, ferments galactose, catalase positive, motile, alkaline with litmus milk, not hemolytic, H2S negative Citrobacter freundii Gram negative bacillus; acid-fast negative, does not ferment galactose, catalase positive, non-motile, acid produced in litmus milk, not hemolytic, H2S negative Pseudomonas fluorescens Gram negative bacillus, acid-fast negative, does not ferment galactose, catalase positive, non-motile, alkaline in litmus milk, hemolytic, H2S negative Streptococcus pneumoniae Gram positive oval coccus found as streptococci, acid-fast negative, galactose fermentation negative, catalase negative, non-motile, acid in litmus milk, hemolytic, H2S negative Mycobacterium smegmatis Gram positive club-shaped bacilli, acid-fast positive, galactose fermentation negative, catalase-negative,, non-motile, alkaline in litmus milk, catalase positive, not hemolytic, H2S negative Mycobacterium leprae Gram positive club-shaped bacilli, acid-fast positive, galactose fermentation negative, catalase-positive, non-motile, alkaline in litmus milk not hemolytic, H2S negative Corynebacterium xerosis Gram positive club-shaped bacilli, acid-fast negative, galactose fermentation positive, non-motile, acid from litmus milk, catalase positive, not hemolytic, H2S negative Aeromonas hydrophila Gram negative bacilli, acid-fast negative, ferments galactose, catalase positive, motile, acid from litmus milk, not hemolytic, H2S positive

Dichotomous Key to Identifying Eight Bacteria Alcaligenes faecalis Mycobacterium smegmatis Citrobacter freundii Mycobacterium leprae Pseudomonas fluorescens Corynebacterium xerosis Streptococcus pneumoniae Aeromonas hydrophila Gram stain negative positive Alcaligenes faecalis Mycobacterium smegmatis Citrobacter freundii Mycobacterium leprae Pseudomonas fluorescens Corynebacterium xerosis Aeromonas hydrophila Streptococcus pneumoniae Galactose fermentation positive negative Alcaligenes faecalis Citrobacter freundii Aeromonas hydrophila Pseudomonas fluorescens H2S production positive negative Aeromonas hydrophila Alcaligenes faecalis

Table of Characteristics for Eight Bacteria Organism Characteristics Alcaligenes faecalis Gram negative bacillus, acid-fast negative, ferments galactose, catalase positive, motile, alkaline with litmus milk, not hemolytic, H2S negative Citrobacter freundii Gram negative bacillus; acid-fast negative, does not ferment galactose, catalase positive, non-motile, acid produced in litmus milk, not hemolytic, H2S negative Pseudomonas fluorescens Gram negative bacillus, acid-fast negative, does not ferment galactose, catalase positive, non-motile, alkaline in litmus milk, hemolytic, H2S negative Streptococcus pneumoniae Gram positive oval coccus found as streptococci, acid-fast negative, galactose fermentation negative, catalase negative, non-motile, acid in litmus milk, hemolytic, H2S negative Mycobacterium smegmatis Gram positive club-shaped bacilli, acid-fast positive, galactose fermentation negative, catalase-negative,, non-motile, alkaline in litmus milk, catalase positive, not hemolytic, H2S negative Mycobacterium leprae Gram positive club-shaped bacilli, acid-fast positive, galactose fermentation negative, catalase-positive, non-motile, alkaline in litmus milk not hemolytic, H2S negative Corynebacterium xerosis Gram positive club-shaped bacilli, acid-fast negative, galactose fermentation positive, non-motile, acid from litmus milk, catalase positive, not hemolytic, H2S negative Aeromonas hydrophila Gram negative bacilli, acid-fast negative, ferments galactose, catalase positive, motile, acid from litmus milk, not hemolytic, H2S positive

Dichotomous Key to Identifying Eight Bacteria Alcaligenes faecalis Mycobacterium smegmatis Citrobacter freundii Mycobacterium leprae Pseudomonas fluorescens Corynebacterium xerosis Streptococcus pneumoniae Aeromonas hydrophila Gram stain negative positive Alcaligenes faecalis Mycobacterium smegmatis Citrobacter freundii Mycobacterium leprae Pseudomonas fluorescens Corynebacterium xerosis Aeromonas hydrophila Streptococcus pneumoniae Galactose fermentation positive negative Alcaligenes faecalis Citrobacter freundii Aeromonas hydrophila Pseudomonas fluorescens H2S production Litmus milk positive negative acid alkaline Aeromonas hydrophila Alcaligenes faecalis Citrobacter freundii Pseudomonas fluorescens

Table of Characteristics for Eight Bacteria Organism Characteristics Alcaligenes faecalis Gram negative bacillus, acid-fast negative, ferments galactose, catalase positive, motile, alkaline with litmus milk, not hemolytic, H2S negative Citrobacter freundii Gram negative bacillus; acid-fast negative, does not ferment galactose, catalase positive, non-motile, acid produced in litmus milk, not hemolytic, H2S negative Pseudomonas fluorescens Gram negative bacillus, acid-fast negative, does not ferment galactose, catalase positive, non-motile, alkaline in litmus milk, hemolytic, H2S negative Streptococcus pneumoniae Gram positive oval coccus found as streptococci, acid-fast negative, galactose fermentation negative, catalase negative, non-motile, acid in litmus milk, hemolytic, H2S negative Mycobacterium smegmatis Gram positive club-shaped bacilli, acid-fast positive, galactose fermentation negative, catalase-negative,, non-motile, alkaline in litmus milk, catalase positive, not hemolytic, H2S negative Mycobacterium leprae Gram positive club-shaped bacilli, acid-fast positive, galactose fermentation negative, catalase-positive, non-motile, alkaline in litmus milk not hemolytic, H2S negative Corynebacterium xerosis Gram positive club-shaped bacilli, acid-fast negative, galactose fermentation positive, non-motile, acid from litmus milk, catalase positive, not hemolytic, H2S negative Aeromonas hydrophila Gram negative bacilli, acid-fast negative, ferments galactose, catalase positive, motile, acid from litmus milk, not hemolytic, H2S positive

Dichotomous Key to Identifying Eight Bacteria Alcaligenes faecalis Mycobacterium smegmatis Citrobacter freundii Mycobacterium leprae Pseudomonas fluorescens Corynebacterium xerosis Streptococcus pneumoniae Aeromonas hydrophila Gram stain negative positive Alcaligenes faecalis Mycobacterium smegmatis Citrobacter freundii Mycobacterium leprae Pseudomonas fluorescens Corynebacterium xerosis Aeromonas hydrophila Streptococcus pneumoniae Galactose fermentation Acid-fast staining positive negative acid fast not acid fast Mycobacterium smegmatis Corynebacterium xerosis Mycobacterium leprae Streptococcus pneumoniae Alcaligenes faecalis Citrobacter freundii Aeromonas hydrophila Pseudomonas fluorescens H2S production Litmus milk positive negative acid alkaline Aeromonas hydrophila Alcaligenes faecalis Citrobacter freundii Pseudomonas fluorescens

Table of Characteristics for Eight Bacteria Organism Characteristics Alcaligenes faecalis Gram negative bacillus, acid-fast negative, ferments galactose, catalase positive, motile, alkaline with litmus milk, not hemolytic, H2S negative Citrobacter freundii Gram negative bacillus; acid-fast negative, does not ferment galactose, catalase positive, non-motile, acid produced in litmus milk, not hemolytic, H2S negative Pseudomonas fluorescens Gram negative bacillus, acid-fast negative, does not ferment galactose, catalase positive, non-motile, alkaline in litmus milk, hemolytic, H2S negative Streptococcus pneumoniae Gram positive oval coccus found as streptococci, acid-fast negative, galactose fermentation negative, catalase negative, non-motile, acid in litmus milk, hemolytic, H2S negative Mycobacterium smegmatis Gram positive club-shaped bacilli, acid-fast positive, galactose fermentation negative, catalase-negative,, non-motile, alkaline in litmus milk, catalase positive, not hemolytic, H2S negative Mycobacterium leprae Gram positive club-shaped bacilli, acid-fast positive, galactose fermentation negative, catalase-positive, non-motile, alkaline in litmus milk not hemolytic, H2S negative Corynebacterium xerosis Gram positive club-shaped bacilli, acid-fast negative, galactose fermentation positive, non-motile, acid from litmus milk, catalase positive, not hemolytic, H2S negative Aeromonas hydrophila Gram negative bacilli, acid-fast negative, ferments galactose, catalase positive, motile, acid from litmus milk, not hemolytic, H2S positive

Dichotomous Key to Identifying Eight Bacteria Alcaligenes faecalis Mycobacterium smegmatis Citrobacter freundii Mycobacterium leprae Pseudomonas fluorescens Corynebacterium xerosis Streptococcus pneumoniae Aeromonas hydrophila Gram stain negative positive Alcaligenes faecalis Mycobacterium smegmatis Citrobacter freundii Mycobacterium leprae Pseudomonas fluorescens Corynebacterium xerosis Aeromonas hydrophila Streptococcus pneumoniae Galactose fermentation Acid-fast staining positive negative acid fast not acid fast Mycobacterium smegmatis Corynebacterium xerosis Mycobacterium leprae Streptococcus pneumoniae Alcaligenes faecalis Citrobacter freundii Aeromonas hydrophila Pseudomonas fluorescens Catalase produced H2S production Litmus milk positive negative acid alkaline positive negative Aeromonas hydrophila Alcaligenes faecalis Citrobacter freundii Pseudomonas fluorescens Mycobacterium leprae Mycobacterium smegmatis

Table of Characteristics for Eight Bacteria Organism Characteristics Alcaligenes faecalis Gram negative bacillus, acid-fast negative, ferments galactose, catalase positive, motile, alkaline with litmus milk, not hemolytic, H2S negative Citrobacter freundii Gram negative bacillus; acid-fast negative, does not ferment galactose, catalase positive, non-motile, acid produced in litmus milk, not hemolytic, H2S negative Pseudomonas fluorescens Gram negative bacillus, acid-fast negative, does not ferment galactose, catalase positive, non-motile, alkaline in litmus milk, hemolytic, H2S negative Streptococcus pneumoniae Gram positive oval coccus found as streptococci, acid-fast negative, galactose fermentation negative, catalase negative, non-motile, acid in litmus milk, hemolytic, H2S negative Mycobacterium smegmatis Gram positive club-shaped bacilli, acid-fast positive, galactose fermentation negative, catalase-negative,, non-motile, alkaline in litmus milk, catalase positive, not hemolytic, H2S negative Mycobacterium leprae Gram positive club-shaped bacilli, acid-fast positive, galactose fermentation negative, catalase-positive, non-motile, alkaline in litmus milk not hemolytic, H2S negative Corynebacterium xerosis Gram positive club-shaped bacilli, acid-fast negative, galactose fermentation positive, non-motile, acid from litmus milk, catalase positive, not hemolytic, H2S negative Aeromonas hydrophila Gram negative bacilli, acid-fast negative, ferments galactose, catalase positive, motile, acid from litmus milk, not hemolytic, H2S positive

Dichotomous Key to Identifying Eight Bacteria Alcaligenes faecalis Mycobacterium smegmatis Citrobacter freundii Mycobacterium leprae Pseudomonas fluorescens Corynebacterium xerosis Streptococcus pneumoniae Aeromonas hydrophila Gram stain negative positive Alcaligenes faecalis Mycobacterium smegmatis Citrobacter freundii Mycobacterium leprae Pseudomonas fluorescens Corynebacterium xerosis Aeromonas hydrophila Streptococcus pneumoniae Galactose fermentation Acid-fast staining positive negative acid fast not acid fast Mycobacterium smegmatis Corynebacterium xerosis Mycobacterium leprae Streptococcus pneumoniae Alcaligenes faecalis Citrobacter freundii Aeromonas hydrophila Pseudomonas fluorescens Catalase produced Hemolysis H2S production Litmus milk positive acid alkaline negative positive negative positive negative Aeromonas hydrophila Citrobacter freundii Pseudomonas fluorescens Alcaligenes faecalis Mycobacterium leprae Mycobacterium smegmatis Streptococcus pneumoniae Corynebacterium xerosis