INTRODUCTION TO MICROBIOLOGY - Lesson 1 Flashcards
Lesson 1
the scientific study of microorganisms
MICROBIOLOGY
minute living things that individually are usually too small to be seen with the unaided eye
Microorganisms
Types of Microorganisms
- Bacteria
- Fungi
- Protozoa
- Algae
- Viruses
- aka microbiota
MICROBIOME
- microbes that live stably in and on the human body
MICROBIOME
types of microbiota
- normal microbiota– indefinitely colonize the body
- transient microbiota– transiently colonize the body
Parts of a Prokaryotic Cell
- Glycocalyx
- Cell Appendages
-* Flagella
-* Axial filaments
-* Fimbriae
-* Pili - Cell Wall
- Plasma Membrane
- Cytoplasm
- Ribosomes
- Inclusions
- Nucleoid
- Endospores
- “sugar coat”
- a viscous (sticky), gelatinous polymer that is external to the cell wall
Glycocalyx
- composed of polysaccharide, polypeptide, or both
- made inside the cell and secreted to the cell surface
- 2types
- Capsule
- Slime layer
Glycocalyx
- contributes to bacterial virulence
- protects pathogenic bacteria from phagocytosis
Capsule
- long filamentous appendages that propel bacteria
Flagella
– movement of bacterium toward or away from a particular stimulus
* Chemotaxis
* Phototaxis
Taxis
- aka endoflagella
Axial Filaments
- bundles of fibrils that spiral around the cell
- structure for motility in spirochetes
Axial Filaments
- arise and anchored at the ends of the cell beneath an outer sheath
- similar structure to flagella
Axial Filaments
- hairlike appendages that are shorter, straighter, and thinner than flagella
- consist of a protein called pilin arranged helically around a central core
- present in manyg(-)bacteria
Fimbriae and Pili
- a few to several hundred per cell
- adhere to surfaces
Fimbriae
- longer and fewer than fimbriae (1-2/cell)
- for motility and DNA transfer (e.g. sex pili in conjugation)
Pili
- complex, semirigid structure
Functions:
* prevents bacterial cell rupture
* maintain shape of bacterium
* point of anchorage for flagella
Cell Wall
- present in all bacteria, except Mycoplasma and Ureaplasma
Cell Wall
- contributes to the ability to cause disease
- the site of action of some antibiotics
- differentiates major types of bacteria based on composition
Cell Wall
- composed of peptidoglycan (aka
murein) alone or in combination with
other substances - repeating disaccharide: acetylglucosamine
(NAG) acetylmuramicacid(NAM) - polypeptides
Cell Wall
- many layers of peptidoglycan, forming a thick, rigid structure
Gram-Positive Cell Wall
- one or very few layers of peptidoglycan and an outer membrane
Gram-Positive Cell Wall
Contains lipopolysaccharide (LPS) and Periplasmic Space
Gram-Positive Cell Wall
lipids and carbohydrates
lipopolysaccharide (LPS)
– released when g(-) bacteria die; causes fever,
shock, blood clotting, dilation of blood vessels)
Lipid A (Endotoxin)
structural function
Core polysaccharide
functions as antigen
- *also present in Listeria monocytogenes (a gram-positive bacteria) but does
not function as endotoxin
O polysaccharide
between inner membrane and outer
membrane
Periplasmic Space
- present in Mycobacterium and Nocardia
- contains high concentrations (60%) of a hydrophobic waxy lipid
(mycolic acid) - e.g., in Mycobacterium and Nocardia
Acid-Fast Cell Wall
- inside the cell wall and encloses the cytoplasm
- consists mainly of phospholipids, proteins, glycoproteins, glycolipids
- lacks sterols, except Mycoplasma and Ureaplasma
Plasma Membrane
- Structure: Fluid Mosaic Model
-* Lipid Bilayer
-* Membrane Proteins - Function: selective barrier
Plasma Membrane
- the substance of the cell inside the plasma membrane
- ≈80% H2O and contains primarily proteins (enzymes), carbohydrates, lipids, ions, and many LMW compounds
- contains the cytoskeleton, nucleoid, ribosomes, and cytoplasmic inclusions
Cytoplasm
- site of protein synthesis
- gives the cell a granular appearance
- consists of protein and rRNA
- 2subunits (70s):
- Large(50s)
- Small(30s)
Ribosomes
Inclusions
- Metachromic granules –inorganic phosphate (polyphosphate) that can be used in the synthesis of ATP
- Polysaccharide granules – glycogen and starch
- Lipid inclusions – lipid
- Sulfur granules – sulfur and S-containing compounds
- Carboxysomes–ribulose 1,5-bisphosphate carboxylase
- Gas vacuoles – hollow cavities
- Magnetosomes–ferric oxide
- nonuclear envelope
- contains asingle long, continuous, and circularly double-stranded
DNAcalledthebacterial chromosome- nohistones
- attached totheplasmamembrane
- nohistones
Nucleoid
- extrachromosomal DNA
- small usually circular, double-stranded DNA
- replicate independently from chromosome
- notcrucial for survival but adds some advantages
Plasmid
- specialized“resting”cells
- highly durable dehydrated cells with thick walls and additional layers
- can survive extreme heat, lack of water, and exposure to many toxic chemicals and radiation
- resistant to processes that kill vegetative cells (e.g. desiccation, chemicals, radiation, heating)
Endospores
- formedinternal to the cell membrane
- contains high amounts of dipicolinic acid (DPA), and calcium
ions - present in Clostridium and Bacillus
Endospores
- Sporulation/Sporogenesis– spore formation
- Germination–return of endospore to vegetative state
Endospores
The Three Domains of Life
Bacteria
Archeaa
Eukarya
Five Kingdoms
Fungi
Plants
Animals
Protista
Monera
Prokaryotes 2 types
Bacteria
Archaeabacteria
– unicellular prokaryotes; have peptidoglycan cell walls; reproduce by binary fission
Bacteria
- live in extreme environments and carry
out unusual metabolic processes; no peptidoglycan in cell walls - Methanogens– obligate anaerobes that produce CH4 from CO2 and H2
- Extremehalophiles– requiremhigh concentrations of salt for survival
- Hyperthermophiles–grow in extremely hot nenvironments
Archaeabacteria
3 types of Eukaryotes
Fungi, Protists, Animal Parasites
– may be unicellular (yeasts) or multicellular (moldsand mushrooms; form hyphae); have chitin cell walls; reproduce sexually (meiosis) or asexually (spores)
Fungi
– eukaryotes that are not plants, fungi, or animals
- Protozoa– unicellular nonphotosynthetic protists; reproduce sexually or asexually
- Algae– unicellular photosynthetic protists; have cellulose cell walls; reproduce sexually and asexually
Protists
–multicellular eukaryotes
* Flatworms
* Roundworms
Animal Parasites
- acellular obligatory intracellular parasites
- Structure:
- single type of nucleic acid, either DNA or RNA
- protein coat (sometimes enclosed by an envelope) that surrounds
the nucleic acid - multiply inside living cells by using the synthesizing machinery of
the cell
Viruses
- infectious proteinaceous particle
Prions
