3.01 Bacteria Basics

Microbio review for the USMLE Step 1 Exam:

• Bacteria are single-celled organisms that can cause infection
• Structural components of bacteria include: capsule, cell wall, flagella, fimbriae, plasma membrane, ribosomes, endospores, and DNA
• Capsules help bacteria evade the immune system by inhibiting phagocytes
• Flagella are tail-like appendages that allow bacteria to move, fimbriae help bacteria adhere to surfaces
• Most bacteria have a cell wall, which can be either gram positive or gram negative
• Plasma membrane is composed of proteins and phospholipids and performs various functions
• DNA is the genetic material, ribosomes are used to build proteins, some bacteria have endospores which are heat-resistant resting cells
• Bacteria can be classified by cell wall composition, morphology, metabolism, and based on their ability to grow at different temperatures and pH levels
• Gram staining is a laboratory technique used to differentiate between gram positive and gram negative bacteria
• Morphology of bacteria includes cocci (spherical), bacilli (rod-shaped), and spirilla (spiral-shaped)
• Metabolism of bacteria can be aerobic (uses oxygen) or anaerobic (doesn't use oxygen)
• Temperature and pH ranges at which bacteria can grow vary widely, some can grow at extreme conditions
• Pathogenic bacteria cause disease, while non-pathogenic bacteria do not
• Bacteria can be treated with antibiotics, but overuse can lead to antibiotic resistance