Biochemistry I Labs 22,23,24

Exoenzymes – Lab 22 Bacteria make enzymes to digest macromolecules outside of the cell The smaller sub units of the enzymatic reaction are then able to be transported across the cell membrane This capacity is a characteristic of many Gram Positive bacteria

Hydrolysis of starch Starch is composed of glucose molecules connected by glycosidic linkages When the glycosidic linkages are broken, individual sugar molecules are produced Linkages are broken in the presence of Water and the enzyme amylase

Hydrolysis of Gelatin When water and an enzyme are added to a protein, the peptide bond in proteins are broken, producing individual amino acids

Gelatin Hydrolysis in the tube

Carbohydrates and Sugars

Glycolysis

Sugar fermentation- Carbohydrate metabolism

Fermentation Phenol red – pH indicator is red in a neutral environment and yellow is the result of an acidic pH Gas – Gas is a by - product of the fermentation reaction -

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Triple Sugar Iron a. metabolize lactose and/or sucrose b. conduct fermentation to produce acid c. produce gas during fermentation d. generate H2S.

TSI Results

Results BUTT COLOR/CO NDITION Cod e Lett er InterpretationExample REDR no fermentation, the bacterium is an obligate aerobe Example red butt YELLOWY some fermentation has occurred, acid has been produced, it is a facultative anaerobe. Example yellow butt GAS FORMED YG Seen as cracks in the agar, bubbles, or the entire slant may be pushed out of the tube. (Caution: these gassy fermenters may have bacteria close to the opening.) Example yellow butt with gas BLACK"+""+"H 2 S has been produced Example black butt

SLANTBUTTH2SH2SCOMMENTS Shigella dysenteriae RY Causes food infection dysentery Salmonella typhimurium RYG+ Causes food poisoning Salmonella typhi RY+ Causes typhoid fever Aerobacter aerogenes YYG Similar to Klebsiella,but nonrespiratory Escherichia coliYYG Most common of GIflora Citrobacter freundii YYG+ one of "paracolon" group (non- pathogenic) Proteus vulgarisYYG + Causes GU infections, highly motile Klebsiella pneumoniae Y R or YG Pneumonia in debilitated patients (nosocomial) Pseudomonas aeruginosa RR GI inhabitant, causes wound, GU infections Alcaligenes faecalis RR GI inhabitant, opportunistic pathogen of GU