Bacteriology exam prep 1-3

History of Microbiology

• Microbiology is the study of microorganisms, including bacteria, fungi, algae, protozoa, and viruses
• Antonie van Leeuwenhoek (1632-1723) is considered the "father of microbiology" and was the first to document microscopic observations of microorganisms
• Robert Hooke (1635-1703) was an English polymath who discovered the law of elasticity and was one of the first to discover microorganisms using a microscope
• Edward Jenner (1749-1823) pioneered the concept of vaccines and developed the first vaccine against smallpox
• Louis Pasteur (1822-1895) was a French chemist and microbiologist who developed the principles of vaccination, microbial fermentation, and pasteurization
• Robert Koch (1843-1910) was a German physician and microbiologist who discovered the causative agents of tuberculosis, cholera, and anthrax

Notable Latvian Scientists in Microbiology

• Kristaps Helmanis (1848-1892) discovered tuberculin simultaneously with Robert Koch
• Oto Kalniņš (1856-1891) discovered mallein together with Kristaps Helmanis
• Augusts Kirhenšteins (1872-1963) was a Latvian microbiologist, politician, and educator who contributed to the development of science in Latvia, especially in microbiology, immunology, dairy farming, and biotechnology

Bacteriology

• Bacteriology is the study of the morphology, ecology, genetics, and biochemistry of bacteria
• General characteristics of bacteria:
  • Ubiquitous in nature
  • Single-celled microscopic organisms
  • Can be harmful or beneficial to the host
• Classification of bacteria involves taxonomy, identification, and nomenclature
• Growth properties of bacteria include growth on media, motility, aerobic/anaerobic growth, and temperature tolerance

Bacterial Anatomy and Physiology

• Bacterial cell size ranges from 0.2-2 μm in diameter and 2-8 μm in length
• Basic shapes of bacteria include spherical, rod-shaped, and spiral
• Typical arrangements of bacteria include tetrads, diplococci, and streptobacilli
• Structures of bacterial cell include cell envelope, cytoplasmic membrane, cell wall, and cytoplasm
• Cell walls of gram-positive bacteria have a thick peptidoglycan layer, while gram-negative bacteria have a thin peptidoglycan layer and an outer membrane
• Cytoplasmic structures include nucleoid, ribosomes, inclusions, plasmids, and spores
• Surface structures include capsule, slime layer, flagella, and fimbriae/pili

Gram Staining Method

• The Gram staining technique is used to categorize bacteria into gram-positive or gram-negative
• The stain allows determination of cell morphology and shape
• Gram-positive bacteria have a thick peptidoglycan layer, while gram-negative bacteria have a thin peptidoglycan layer and an outer membrane

Bacterial Physiology, Metabolism, Growth, and Nutrition

• Metabolism involves energy production mechanisms, including fermentation and respiration

• Bacterial growth involves an increase in the number of cells, not in their size

• The growth curve includes lag phase, logarithmic phase, stationary phase, and death phase

• Bacterial nutrition requires oxygen, carbon dioxide, temperature, pH, nutrients, and growth factors### Anaerobes

• Anaerobes are categorized into two types based on their oxygen tolerance:

  • Aerotolerant anaerobes: do not grow in the presence of oxygen but survive exposure to oxygen for a short period (minutes to hours)
  • Obligate anaerobes: inhibited or killed by exposure to oxygen

Environmental Requirements

• CO2: required for normal biosynthetic reactions; some bacteria require elevated levels (capnophiles)
• pH: most pathogenic bacteria grow best at a neutral pH (range 6.8-7.2)
• Temperature: bacteria are categorized into three groups based on their optimal temperature for growth:
  • Psychrophiles: grow best at 10-15°C (range 0-25°C)
  • Mesophiles: grow best at 30-37°C (range 15-45°C)
  • Thermophiles: grow best at 55°C (range 35-70°C)
• Ionic strength/osmotic pressure: most pathogenic bacteria grow best at osmotic pressures equivalent to physiological saline, but some can tolerate or grow at high salt concentrations

Nutrients for Growth

• Macronutrients: C, N, P, S, K, O, H (constitute 95% of dry cell weight)
• Micronutrients: Cu, Fe, Mn, Mo, Zn, Ni (required for enzymes, cofactors, and vitamins)
• Growth factors: specific vitamins, amino acids, purines, and pyrimidines required in small amounts by some bacteria

Staining of Bacteria

• Ziehl-Neelsen method: used to stain acid-fast bacteria (e.g., Mycobacterium)
• Schaeffer-Fulton method: used to stain endospores (e.g., Bacillus spp. and Clostridium spp.)
• Anthony's method: used to stain capsules (the polysaccharide, mucus-like layer around bacterial cells)
• Staining process: heat-fixation, primary stain, decolorizing agent, and counterstain are used to differentiate bacteria

Cultivation of Bacteria

• Cultivation: the process of propagating organisms by providing proper environmental conditions
• Requirements for growth: nutrients, pH, temperature, aeration, salt concentration, and ionic strength
• Media: a specifically prepared environment in the laboratory that ensures the preservation, growth, and reproduction of bacteria
• Media composition: nutrients, energy source, essential metals and minerals, buffering agents, indicators, selective agents, and gelling compound (agar-agar)
• Classification of media: based on composition, consistency, and purpose