Gram Positive and Negative Bacteria Quiz

Gram Positives

• Gram-positive bacteria have a thick layer of peptidoglycan in their cell walls
• They lack an outer membrane
• They often contain teichoic acids
• Examples include Bacillus, Streptococcus, and Staphylococcus

Classifying Prokaryotes

• Prokaryotes are categorized into two domains: Bacteria and Archaea
• Bacteria are further divided into phyla, such as Pseudomonadota, Bacteroidota, Chlamydiota, Cyanobacteriota, Spirochetota, Bacillota, and Actinomycetota
• Bacillota (Firmicutes) is a significant component of the human gut microbiome
• Actinomycetota (Actinobacteria) is associated with soil and nitrogen fixation
• Pseudomonadota and non-Pseudomonadota are related groups of Gram-negative bacteria.

Gram Positive vs. Gram Negative

• Gram-positive bacteria have a thick peptidoglycan layer and lack an outer membrane.
• Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane containing lipopolysaccharides
• Gram-positive bacteria often have teichoic acid in their cell wall.

Phylum: Bacillota (Firmicutes)

• Low GC content

• Often obligate or facultative anaerobes

• Important component of the human intestinal microbiome

• Number may decrease with age and is possibly linked to obesity

• Order: Lactobacillales

  • Low GC content
  • Bacteria that tolerate or exist in acidic conditions
  • Examples: Streptococcus, Lactobacillus,
  • Used in food industry (yogurt, cheese, wine) & as probiotics
  • Some species can cause disease

• Order: Bacillales

  • Common in soil
  • Anaerobic, facultative aerobic
  • Spore-formers

Staphylococcus aureus

• Causes a wide range of diseases, including skin infections, food poisoning, and toxic shock syndrome
• Widely distributed in the environment and 25% of the population are carriers
• Causes hospital acquired infections
• Produces toxins, such as enterotoxins, leading to food poisoning and other diseases
• Resistant to some antibiotics (MRSA)

Bacillus thuringiensis

• Produces insecticidal toxins used as natural pesticides
• Pesticides based on these toxins are considered safe for the environment
• Used to control insect pests, particularly blackflies which act as vectors
• Used in genetically engineered crops (GM crops)

Bacillus anthracis

• Causes anthrax, a serious disease that can affect livestock and humans.
• Different forms of anthrax (cutaneous, pulmonary, gastrointestinal) have different levels of mortality
• Can be weaponized

Clostridium botulinum

• This bacterium creates botulism, especially in canned foods.
• Its toxin affects the neuromuscular system, causing muscle weakness and paralysis.
• Antitoxin is used to counteract it, and this bacterium also has medical applications, including treatment of muscle spasms and cosmetic uses.

Phylum: Actinomycetota (Actinobacteria)

• High GC content
• Mostly terrestrial or lives in aquatic environments.
• Important in the soil, nitrogen fixation
• Several are pathogens

Streptomyces

• Largest genus of actinobacteria
• A major source of antibiotics, including streptomycin, chloramphenicol, and tetracycline
• Soil dwelling, aerobic and spore-forming
• Produce geosmin, a compound that gives soil its earthy smell

Mycobacterium

• Cannot be stained using Gram staining technique
• Slow-growing aerobic bacteria
• Two notable pathogens: Mycobacterium tuberculosis (TB), a lung infection, and Mycobacterium leprae (leprosy), affecting the skin and peripheral nerves.
• TB & Leprosy are socially stigmatic infections due to the slow-growing nature of the bacteria