Describe the differences in growth of Pseudomonas aeruginosa in nutrient agar slant.
The correct answer and explanation is:
Pseudomonas aeruginosa is a versatile and opportunistic bacterium that grows well on nutrient agar slants, showing distinct features based on the conditions of the culture. The growth of P. aeruginosa can be influenced by several factors, including the medium composition, temperature, and atmospheric conditions.
On a nutrient agar slant, Pseudomonas aeruginosa typically grows as a smooth, moist, and glossy colony, with a characteristic blue-green pigmentation due to the production of pigments such as pyocyanin and pyoverdine. The colony can be opaque or slightly translucent, and the appearance of the pigment can vary from light to dark green depending on the strain and conditions.
Growth on the slant is usually spread along the surface, forming a confluent growth pattern, which is often smooth or slightly wrinkled in appearance. The growth at the base of the slant might be denser, with more extensive pigmentation. In some cases, the bacterium may exhibit a “fuzzy” or “feathery” edge as it spreads from the inoculation point.
The slant’s angle plays a role in growth patterns, with the upper region (exposed to more oxygen) showing a more pronounced development of the green pigment. Additionally, the slant’s surface may have a characteristic fruity or grape-like odor due to the production of volatile organic compounds by P. aeruginosa.
Temperature can significantly affect the growth of P. aeruginosa. At higher temperatures, such as 37°C, the bacterium grows optimally, and the color intensifies. At lower temperatures, the growth may still be observed, but pigmentation and colony morphology could be less pronounced.
In summary, the growth of Pseudomonas aeruginosa on nutrient agar slants is characterized by its distinctive blue-green pigmentation, smooth, glossy colony morphology, and often fruity odor. Factors like temperature, oxygen availability, and medium composition can all influence its growth pattern and appearance on the slant.