MacConkey agar is designed to grow Gram-negative bacteria and also contains crystal violet dye which inhibits the growth of Gram-positive bacteria. Since S. aureus is Gram-positive it should not grow on MacConkey agar. No. MacConkey agar inhibits MOST of the Gram-positive bacteria. There are some Gram-positive bacteria that can tolerate bile-salt are able to grow in MacConkey agar. Enterococcus and some species of Staphylococcus are able to grow in MacConkey. (lack citation though)
Yes, Micrococcus luteus is a facultative anaerobe, meaning it can grow in both the presence and absence of oxygen. It has the ability to switch between aerobic and anaerobic metabolism depending on the availability of oxygen in its environment.
Enterococcus faecalis typically does not grow on MacConkey agar as this selective and differential medium is primarily used for isolating and differentiating members of the Enterobacteriaceae family, which are mostly gram-negative bacteria. Enterococcus species are gram-positive bacteria and do not ferment lactose, the key ingredient in MacConkey agar that allows for differentiation.
E. coli that grow on MacConkey agar typically exhibit lactose fermentation, causing them to produce pink or red colonies. These colonies may also appear mucoid due to the production of a polysaccharide capsule. Additionally, E. coli on MacConkey agar will typically not grow well under acidic conditions, as the agar contains crystal violet which inhibits the growth of Gram-positive bacteria.
The yellow bacteria that grows on agar and feeds on oatmeal with a drop of water is likely the species Micrococcus luteus. This bacterium is commonly used in laboratory settings for its distinctive yellow pigmentation and ability to grow on simple media like agar and oatmeal.
Micrococcus luteus is negative for oxidase because it lacks the cytochrome c oxidase enzyme necessary to produce a positive oxidase reaction. The absence of this enzyme prevents the organism from undergoing the oxidation-reduction reaction typically measured by an oxidase test.
No, Alcaligenes faecalis will not grow on MacConkey agar. MacConkey agar is selective for gram-negative bacteria that ferment lactose. Alcaligenes faecalis is a gram-negative bacteria that does not ferment lactose, so it will not grow on MacConkey agar.
Micrococcus luteus is not commonly found on Mannitol Salt Agar (MSA) plates because M. luteus is not a halophilic bacteria that thrives in high salt conditions, which are present in MSA. However, it is always possible for environmental isolates to vary so it's best to perform a culture test to confirm its growth on MSA plates.
MacConkey agar
Yes, Micrococcus luteus is a facultative anaerobe, meaning it can grow in both the presence and absence of oxygen. It has the ability to switch between aerobic and anaerobic metabolism depending on the availability of oxygen in its environment.
Enterococcus faecalis typically does not grow on MacConkey agar as this selective and differential medium is primarily used for isolating and differentiating members of the Enterobacteriaceae family, which are mostly gram-negative bacteria. Enterococcus species are gram-positive bacteria and do not ferment lactose, the key ingredient in MacConkey agar that allows for differentiation.
No, Staphylococcus does not typically grow on MacConkey agar, regardless of the absence of crystal violet. MacConkey agar is selective for Gram-negative bacteria like Escherichia coli, and inhibitory to most Gram-positive species.
Gram-negative bacteria that do not grow on MacConkey agar and Eosin Methylene Blue agar include: Helicobacter pylori Neisseria gonorrhoeae Haemophilus influenzae
E. coli that grow on MacConkey agar typically exhibit lactose fermentation, causing them to produce pink or red colonies. These colonies may also appear mucoid due to the production of a polysaccharide capsule. Additionally, E. coli on MacConkey agar will typically not grow well under acidic conditions, as the agar contains crystal violet which inhibits the growth of Gram-positive bacteria.
You would expect the organism to grow better on nutrient agar because it is a general-purpose medium that supports the growth of a wide range of organisms. MacConkey agar, on the other hand, contains inhibitors that selectively inhibit the growth of Gram-negative bacteria, so the organism may not grow as well on this medium.
The yellow bacteria that grows on agar and feeds on oatmeal with a drop of water is likely the species Micrococcus luteus. This bacterium is commonly used in laboratory settings for its distinctive yellow pigmentation and ability to grow on simple media like agar and oatmeal.
Moraxella is a fastidious organism and may grow on MacConkey agar, but not as well as it would on media specifically designed for its growth, such as blood agar. MacConkey agar is selective for Gram-negative bacteria that ferment lactose, which may not support the growth of Moraxella well as it is usually non-lactose fermenting.
MacConkey's agar refers to a culture medium that is designed to selectively grow Gram-negative bacteria. It contains crystal violet dye, which inhibits certain Gram-positive bacteria.