Monika Kumar

 Identification of Bacteria: Staphylococcus epidermidis Bio Lab Report: Throat Bacteria Staphylococcus epidermidis Table of Identification Test Observation Result Explanation Organism(s) Indicated Gram Staining Purple-stained round cells present as cluster and branches Gram-positive cocci Bacteria have thick peptidoglycan cell wall with polysaccharides, teichoic acids and proteins and therefore retain the chemical dye crystal violet. Staphylococcus aureus Or Staphylococcus epidermidis Hemolysis Blood Agar (TSA with 5% Sheep’s Blood) Blood cells are intact and no hemolysis is observed Gamma hemolysis Blood agar is a differential medium that differentiates bacteria by their ability to lyse RBCs and cause hemolysis. This is due to the characteristic property of the bacteria to produce an exoenzyme hemolysin Staphylococcus epidermidis Mannitol Salt Agar Bacteria show positive growth but do not show fermentation Mannitol sugar promotes growth, but it is not fermented by bacteria and pH 7 is retained (red color) Mannitol fermentation is an alternative anaerobic pathway to make ATP by reducing pyruvate and this generates acidic by-products. These by-products alter the pH of the medium and is depicted by the change in color of the medium from red to yellow Staphylococcus epidermidiscannot ferment mannitol and therefore no change in color of medium is observed DNAse Cloudy appearance around the bacterial growth No DNAse production was seen DNAse is produced by bacteria to degrade any DNA (transformed) in the environment and utilize the by-products for DNA biosynthesis. Cloudy appearance on poring HCl shows no DNAse production while clear zone indicates production of DNAse Staphylococcus epidermidis Catalase Oxygen gas is evolved on pouring H2O2 Catalase is produced by the bacteria H2O2 is a toxic by-product of aerobic respiration and bacteria converts it into non-toxic water and oxygen gas in the presence of enzyme catalase. Production of oxygen is observed in the form of bubbles Staphylococcus aureus and Staphylococcus epidermidis Coagulase Coagulase activity in the form of halo is not observed Bacteria is not capable of producing coagulase Enzyme coagulase acts on blood protein fibrinogen and forms fibrin, the clot. This encloses bacteria and thus provides protection, a hiding place and escape from immune system and antibiotic treatment. Thus, bacteria have better survival ability and virulence. Staphylococcus epidermidis