What are the colony characteristics (elevation, margin, whole colony, color, size, surface characteristics, texture and optical properties (opaque or translucent)) of Lactococcus Lactis?
The correct answer and explanation is:
Lactococcus lactis is a gram-positive bacterium that is commonly found in fermented dairy products. The colony characteristics of Lactococcus lactis on agar plates can be described as follows:
- Elevation: Colonies of Lactococcus lactis are generally flat to slightly raised. They do not have significant elevation and appear more or less at the same level as the surrounding medium.
- Margin: The margins of Lactococcus lactis colonies are typically smooth and well-defined. The edges do not appear irregular or jagged, which distinguishes them from some other bacterial species.
- Whole Colony: Lactococcus lactis colonies appear circular in shape and are relatively uniform in size. The colonies are typically small, with a diameter of 1–2 mm when grown on standard agar plates.
- Color: The color of Lactococcus lactis colonies is usually white or creamy. The colonies do not show significant pigmentation, which is typical of many lactic acid bacteria.
- Size: The colonies are small, typically ranging between 1 mm and 2 mm in diameter. This small size is characteristic of Lactococcus lactis and is seen under optimal growth conditions.
- Surface Characteristics: The surface of Lactococcus lactis colonies is typically smooth, without any visible texture such as wrinkles or ridges. The smooth surface indicates the absence of extracellular polysaccharide production, which is common in other bacterial species that form mucoid colonies.
- Texture: The texture of Lactococcus lactis colonies is smooth and moist. The colonies do not appear dry or rough, and they may have a slightly glistening appearance due to moisture.
- Optical Properties (Opaque or Translucent): Lactococcus lactis colonies are opaque, meaning they do not allow light to pass through them. The opaque nature is due to the density and uniformity of the colony structure.
In summary, Lactococcus lactis colonies are small, white, smooth, and opaque with well-defined edges. These characteristics make them relatively easy to identify on agar plates, especially when compared to other bacteria that may produce more pigmented or irregular colonies.