The Gram-Positive bacteria are represented by the phyla Actinobacteria and Firmicutes. They are most common in soil and sediment. The difference between the two phyla is based on the levels of guanine + cytosine (G+C) in the organisms. The Actinobacteria have high levels of G+C while the Firmicutes have low levels.

Resources: Gram-Positive Bacteria and Relatives. James W. Brown. North Carolina State University. http://www.mbio.ncsu.edu/JWB/MB409/lecture/lecture14/lecture14.html. Spring, 2002.

"These are primarily soil organisms, but some are pathogens or opportunistic pathogens. All are aerobic heterotrophs." (Brown, 2002)

• Arthrobacter - common in soil
• Micrococcus luteus
• Streptomyces - produces antibiotics
• Corynebacterium diphtheriae - causes diphtheria
• Frankia
• Propionibacteria
• Bifidobacterium
• Mycobacterium leprae - causes leprosy
• Mycobacterium tuberculosis - causes tuberculosis
• Nocardia

In the Firmicutes, endospore formation is common. These spores form in response to poor environmental conditions. The cell goes dormant until conditions are better, and examples have been found in fossil amber and halite millions of years old. These spores were revived when subjected to the right environment.

• Bacillus - some antibiotics
  • Bacillus cereus
  • Bacillus anthracis - causes anthrax
  • Bacillus clausii
  • Bacillus halodenitrificans
• Clostridium botulinum - anaerobic, found in soil, causes botulism
• Clostridium tetani - causes tetanus
• Epulopiscium fishelsoni - very large prokaryote
• Lactobacillus - make cheese from milk
• Leuconostoc
• Selenomonas
• Staphylococcus - cocci clusters, food poisoning (produce toxins)
  • Staphylococcus aureus - some strains are resistant to methicillin (MRSA) and vancomycin
  • Staphylococcus epidermidis
• Streptococcus - cocci chains, make some foods, disease-causing
  • Streptococcus pneumoniae - can cause meningitis
• Mycoplasma
• Alloiococcus

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