Question

Which one of the following does not belong with the others? a. Enterococcus d. Streptococcus b. Lactobacillus e. All are grouped together. c. Staphylococcus

Short answer

Lactobacillus does not belong with the others.

Step-by-step solution

Analyze the Options

The options given are strains of bacteria: Enterococcus, Streptococcus, Lactobacillus, and Staphylococcus. We need to determine any characteristics or classifications that group some together while excluding others.

Group by Gram Reaction

Explore whether these bacteria are Gram-positive or Gram-negative. Enterococcus, Streptococcus, and Staphylococcus are Gram-positive cocci, while Lactobacillus is a Gram-positive bacillus.

Group by Shape

Check the shape of these bacteria. Enterococcus, Streptococcus, and Staphylococcus are spherical (cocci), whereas Lactobacillus is rod-shaped (bacillus).

Determine Which Stands Out

Identify that while Enterococcus, Streptococcus, and Staphylococcus share both Gram reaction and shape, Lactobacillus is different in shape, making it the one that does not belong in the group with the others.

Key concepts

Gram-positive bacteria

Gram-positive bacteria are a major category of bacteria which are characterized by their cell wall structure. They have a thick peptidoglycan layer that retains the crystal violet stain used in the Gram-staining procedure, which gives them a purple appearance under a microscope. Understanding this classification helps in identifying and categorizing bacteria.

Gram-positive bacteria include many significant genera such as:

• Staphylococcus - Often found on the skin and known for its role in various infections.
• Streptococcus - Associated with illnesses such as strep throat and impetigo.
• Enterococcus - Commonly found in the gastrointestinal tract and can be opportunistic pathogens.
• Lactobacillus - Generally non-pathogenic and important in the production of yogurt and other fermented products.

Knowing these details not only contributes to understanding medical microbiology but also to practical applications in food technology.

Cocci and Bacilli

Bacterial classification often involves considering the shape of the cells, with particular attention to cocci and bacilli.

Cocci are bacteria that have a spherical shape. Their arrangement can vary:

• Staphylococci - These form clusters, resembling grape bunches. They are notorious for skin and soft tissue infections.
• Streptococci - Known for their chain-like formations, they are responsible for many respiratory tract infections.
• Enterococci - These may form pairs or short chains and are more resistant to harsh environments.

In contrast, bacilli are rod-shaped bacteria. A typical example is:

• Lactobacillus - A genus which includes species important in maintaining gut health and in the production of fermented foods.

Understanding these shapes and their arrangements helps microbiologists predict bacterial behavior and potentially their pathogenicity.

Bacterial morphology

Bacterial morphology refers to the size, shape, and arrangement of bacterial cells which is a critical aspect for classification. Each type of morphology provides clues about the bacterium's identity and its potential environmental interactions.

The main morphologies include:

• Cocci - Spherical in shape, and include bacteria like Staphylococcus which are known for certain skin infections.
• Bacilli - Rod-shaped, as seen in the Lactobacillus genus, important in food processing.
• Spirilla - Spiral-shaped bacteria, which are less common in practice but notable for their unique swimming motility.

A deeper understanding of bacterial morphology also aids in laboratory identification and treatment planning, providing essential parameters for distinguishing between different bacterial species. This tangible information is incredibly valuable in clinical microbiology and infectious disease management.