Lecture 5 Bacterial Morphology and Bacterial Anatomy Flashcards
small, microscopic, unicellular, prokaryotic organisms that do not have membrane-bound organelles and lack a true nucleus
derived from ancient Greek word “backerion” meaning “cane” because 1st bacteria observed were bacilli
bacteria
study of bacteria and branch of microbiology
bacteriology
Bacterial Morphology
A. Size
- 0.2-1.5 micrometers in diameter and 3-5 micrometers in length
B. Shape
- coccus, bacillus, or spiral
C. Arrangement
- cocci, bacilli, others
SSA
Bacterial Morphology
A. Size
Bacteria typically range from - micrometers in diameter and about - in length
0.2-1.5 mu m diameter
3-5 mu m length
Bacterial Morphology
A. Size
- Smallest bacteria (~0.2 micrometers)
Mycoplasma species
Bacterial Morphology
A. Size
- Longest bacteria (about 1 cm long)
Thiomargarita magnifica
Bacterial Morphology
A. Size
- One of the largest (~750 micrometers)
Epulopiscium fishelsoni
Bacterial Morphology
B. Shape
Cocus (spherical)
Bacillus (rod-shaped)
Spiral (curved or helical)
Bacterial Morphology
B. Shape
- Coccus (spherical) examples
Staphylococcus aureus (clusters)
Streptococcus pyrogenes (chains)
Bacterial Morphology
B. Shape
- Bacillus (rod-shaped) examples
Escherichia coli
Bacillus subtilis
Bacterial Morphology
B. Shape
- Spiral (curved or helical) examples
Treponema pallidum (syphilis)
Helicobacter pylori (stomach ulcers)
Bacterial Morphology
C. Arrangement
a. Cocci Arrangement
- Monococci
- Diplococci
- Streptococci
- Staphylococci
- Tetrads
- Sarcinae
Bacterial Morphology
C. Arrangement
b. Bacilli Arrangement
- Bacillus
- Diplobacilli
- Streptobacilli
- Palisade
- Coccobacilli
Bacterial Morphology
C. Arrangement
c. Others Arrangement
- Spiral
- Curved
Bacterial Morphology
C. Arrangement
a. Cocci Arrangement
Exist as individual cells
- Monococci (Micrococcus luteus)
Bacterial Morphology
C. Arrangement
a. Cocci Arrangement
Cocci arranged in pairs when cocci divide and remain together
- Diplococci (Streptococcus pneumoniae)
Bacterial Morphology
C. Arrangement
a. Cocci Arrangement
Long chains when cells adhere after repeated divisions in one plane
- Streptococci (Streptococcus pyogenes, Streptococcus agalactiae, Enterococcus, and Lactococcus)
Bacterial Morphology
C. Arrangement
a. Cocci Arrangement
Grape like clusters when cocci divide in random planes
- Staphylococci (Staphylococcus aureus, S. saprophyticus)
Bacterial Morphology
C. Arrangement
a. Cocci Arrangement
Square groups of 4 cells when cocci divide in 2 planes (2d)
- Tetrads (Aerococcus urinae)
Bacterial Morphology
C. Arrangement
a. Cocci Arrangement
Cubical packets of 8 of cells when cocci divide in 3 planes (3d cube)
- Sarcinae (Sarcina spp., Clostridium spp.)
Bacterial Morphology
C. Arrangement
b. Bacilli Arrangement
Single unattached rod-shaped bacteria
- Bacillus (Salmonella enterica, Bacillus cereus)
Bacterial Morphology
C. Arrangement
b. Bacilli Arrangement
Bacilli arranged in a pair
- Diplobacilli (Moraxella bovis, Bacillus licheniformis)
Bacterial Morphology
C. Arrangement
b. Bacilli Arrangement
Bacilli arranged in chains
- Streptobacilli (Streptobacillus moniliform)
Bacterial Morphology
C. Arrangement
b. Bacilli Arrangement
Bacilli arranged in fence-like form, resembling the letter V presenting in a cuneiform or Chinese letter arrangement
- Palisade (Corynebacterium diphtheriae)
Bacterial Morphology
C. Arrangement
b. Bacilli Arrangement
Bacilli with rounded ends or oval-shaped
- Coccobacilli (Chlamydia spp., Haemophilus influenzae)
Bacterial Morphology
C. Arrangement
c. Others Arrangement
Long helical-shaped or twisted bacteria
- Spiral (Spirilla spp., Spirochetes spp.)
Bacterial Morphology
C. Arrangement
c. Others Arrangement
Comma-shaped in structure
- Curved/Comma (Vibrio spp.)
Bacterial Anatomy
I. Surface Components
A. Glycocalyx
B. Cell wall
C. Cell membrane
II. Appendages
A. Flagella
B. Pili/Fimbriae
III. Internal Components
A. Cytoplasm
B. Ribosomes
C. Intracytoplasmic inclusions
D. Bacterial nucleus
E. Bacterial spores
SAI
SGCC, AFP/F, ICRIBB
Bacterial Anatomy
Bacterial cell components can be divided into:
a. The outer layer or cell envelope
b. Cellular appendages
Bacterial Anatomy
a. The outer layer or cell envelope consists of 2 components:
- Cell wall
- Cytoplasmic or plasma membrane - beneath cell wall
Bacterial Anatomy
b. Cellular appendages - some bacteria may possess additional structures such as
Capsule
Flagella
Fimbriae
*Glycocalyx (Capsule/Slime Layer)
Bacterial Anatomy
Surface Components
The general term for any network of polysaccharide or protein containing material extending outside of the cell
A. Glycocalyx
Bacterial Anatomy
Surface Components
A. Glycocalyx
Two types
Capsule
Slime Layer
Bacterial Anatomy
Surface Components
A. Glycocalyx (Capsule/Slime layer)
Thick, structured layer providing protection (e.g. Streptococcus pneumoniae evades immune defense)
Capsule
Bacterial Anatomy
Surface Components
A. Glycocalyx (Capsule/Slime layer)
Loosely attached, aiding in biofilm formation (Pseudomonas aeruginosa)
Slime layer
Bacterial Anatomy
Surface Components
A. Glycocalyx (Capsule/Slime layer)
Functions of glycocalyx
Promote attachment to surfaces
Prevent phagocytosis
Protect cell from adverse physcial factors, infective agents
Promote stability of bacterial suspension by preventing aggregation and settling out
Serve as virus receptor
Depot for waste products
Resistance to drying
Bacterial Anatomy
Surface Components
Layer that lies just outside the plasma (cytoplasmic) membrane
Essential for maintaining shape and preventing osmotic lysis
Made of peptidoglycan (murein)
B. Cell wall
Bacterial Anatomy
Surface Components
B. Cell wall
A polymer of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) crosslinked by peptides
Peptidoglycan (murein)
Bacterial Anatomy
Surface Components
B. Cell wall
Cell wall consists of:
- Periplasm (Peptidoglycan)
- Outer membrane
Bacterial Anatomy
Surface Components
B. Cell wall
Functions of the cell wall
- shape and rigidity to cell
- supports weak cytoplasmic membrane against high internal osmotic pressure of protoplasm
- maintain characteristic shape of bacterium
- takes part in cell division
- functions in interactions (e.g. adhesion) with other bacteria and mammalian cells
- provide specific protein and carbohydrate receptors for attachment of some bacterial viruses
Bacterial Anatomy
Surface Components
B. Cell wall
Gram + vs Gram - Cell wall
_ _ bacteria have uniformly dense cell wall consisting of peptidoglycan
Cell wall (peptidoglycan)
Cell membrane
Gram +
Bacterial Anatomy
Surface Components
B. Cell wall
Gram + vs Gram - Cell wall
_ _ bacteria have very thin peptidoglycan layer and an outer membrane
Outer membrane of cell envelope
Periplasmic space
Peptidoglycan layer
Periplasmic space
Cell membrane
Gram -
Bacterial Anatomy
Surface Components
B. Cell wall
Gram + bacteria consists of
- Periplasm (peptidoglycan) - 50-90% of dry weight of wall, thicker and stronger than those of gram -
- Teichoic acid - consists primarily of an alcohol (glycerol or ribitol) and phosphate
a. wall teichoic acid - covalently linked to peptidoglycan
b. membrane teichoic acid (lipoteichoic acid) - covalently linked to membrane glycolipid and concentrated in mesosomes
G + bacterial cell wall is about 80 nm thick, composed mostly of several layers of peptidoglycan
Bacterial Anatomy
Surface Components
B. Cell wall
Gram - bacteria consists of
- Peptidoglycan - single-unit thick, 5-10% DW of wall of gram -
- Outer membrane - bilayered structure external to peptidoglycan
- Lipoprotein - attach cov and noncov to peptidoglycan by their protein portion and to outer membrane by lipid component
- Lipopolysaccharide (LPS) - unique to gram - outer membrane
- lipid A, core polysacc, O antigen
Bacterial Anatomy
Surface Components
B. Cell wall
Cell wall peptidoglycan synthesis
Composed of a overlapping lattice of 2 sugars that are crosslinked by amino acid bridges. Two sugars are:
- N-acetyl glucosamine (NAG)
- N-acetyl muramic acid (NAM) - only found in cell walls of bacteria
- attached to NAM: side chain generally of 4 amino acids L-alanine, D-alanine, D-glutamic acid, Diamino pimelic acid (PMA)
Bacterial Anatomy
Surface Components
B. Cell wall
Steps in Cell Wall Synthesis
- Cytoplasmic Phase (Precursor Synthesis)
a. Formation of UDP-NAM and UDP-NAG
b. Addition of peptide side chains - Membrane Phase (Lipid Carrier Transport)
a. Bactoprenol (Undecaprenyl Phosphate) acts as a transporter
b. Peptidoglycan precursors transporters across the membrane - Extracellular Phase (Cross-Linking)
a. Polymerization of NAM-NAG chains
b. Transpeptidaation (cross-linking of peptides) catalyzed by Penicillin-Binding Proteins (PBPs)
CWS
CME
Bacterial Anatomy
Surface Components
B. Cell wall
Enzymes that are major targets for antibiotic development
- Mur Enzymes (MurA, MurB, MurC) - catalyze precursor synthesis
- Transglycosylases - link sugar chains (NAG-NAM polymers)
- Transpeptidases (PBPs) - form peptide cross-links
Bacterial Anatomy
Surface Components
Thin (5-10 nm thick)
Composed of phospholipids and proteins
The major barrier in the cell, separating inside of cell from outside
Phospholipid bilayer
Head is _ (water loving)
Tails that face interior of cell membrane are _ (water fearing)
C. Cell membrane
Hydrophilic head, hydrophobic head
Bacterial Anatomy
Surface Components
C. Cell membrane
Functions of the cell membrane
- Semipermeable membrane - controlling inflow and outflow of metabolites to and from protoplasm
- Housing enzymes - outer membrane synthesis, cell wall synthesis, assembly and secretion of extra cytoplasmic and extracellular substances
- Housing sensory and chemotaxis proteins that monitor chemical and physical changes in envi
- Generation of chemical energy (e.g. ATP)
- Cell motility
- Mediation of chromosomal segregation during replication
Bacterial Anatomy
Cellular Appendages
Slender threadlike portion, long, hollow, helical filaments (3-20 mu m long)
Originates in bacterial protoplasm, extruded through cell wall
Made of flagellin protein
Typically 5-10 per bacterial cell
Powered by proton motive force (H+ gradient)
A. Flagella
Bacterial Anatomy
Cellular Appendages
A. Flagella
Structures
- Filament - longest and most obvious portion
- Hook - short, curved segment which links filament to basal body
- Basal body - embedded in cell (cytoplasmic membrane)
In gram - bacteria, basal body has 4 rings connected to a central rod (L, P, S, M)
Bacterial Anatomy
Cellular Appendages
A. Flagella
Flagellar Synthesis
If a flagellum is cut off it will regenerate until it reaches a MAX LENGTH
Growth is not from base but from TIP
The filament is HOLLOW, subunits travel through filament and self-assemble at the end
During assembly, protein components are added at flagellar TIP rather than at base
Bacterial Anatomy
Cellular Appendages
A. Flagella
Arrangements
- Monotrichous - single polar flagellum (Vibrio cholerae)
- Amphitrichous - single flagellum at both ends (Alcaligenes faecalis)
- Lophotrichous - tuft of flagella at one or both ends (Spirillum)
- Peritrichous - flagella surrounding cell
-trichus - haair
-lopho - tuft
-amphi - both sides
-peri - around
Bacterial Anatomy
Cellular Appendages
Short, fine, hairlike surface appendages (0.1-1.5 mu m in length and uniform width 4-8 nm)
Shorter and thinner than flagella
Single cells have been seen to be covered with 10-1000 fimbriae
Originate in cytoplasmic membrane, composed of structural protein subunits termed pilins
Occur in nonmotile and motile strains
B. Pili or Fimbriae
Bacterial Anatomy
Cellular Appendages
B. Pili or Fimbriae
Functions of pili or fimbriae
Do not function in motility
Thought to be important in attachment to surfaces or cells sticking together
Bacterial Anatomy
Cellular Appendages
B. Pili or Fimbriae
Two types of pili
- Ordinary (common) pili - organs of adhesions that allow attachment of bacterial cell to other cells or surfaces
- adhesive property may be of value to bacteria in holding them in nutritionally favorable microenvironments - Sex pili - about 1-10 per cell similar to fimbriae but functionally different
- longer and fewer in number than fimbriae
- genetically determined by sex factors or conjugative plasmids, involved in transfer of DNA during conjugation
Bacterial Anatomy
Internal Components
A viscous watery solution or soft gel cell material bounded by cytoplasmic membrane
Composed of 3 areas: _, _, _
A. Cytoplasm
Composed of 3 areas:
a. cytoplasmic area - granular
b. chromatinic area
c. fluid portion - contain inclusion and vacuoles
Bacterial Anatomy
Internal Components
Small, electron-dense particles in cytoplasmic region
Location for all bacterial protein syntheis
Main function: read RNA and synthesize PROTEINS
B. Ribosomes
Bacterial Anatomy
Internal Components
B. Ribosomes
Types of RNA
mRNA - encodes proteins
tRNA - adaptor between mRNA and amino acids
rRNA - forms ribosome
Bacterial Anatomy
Internal Components
Not permanent or essential structures and may be absent under certain conditions of growth
These bodies are usually for storage and reduce osmotic pressure by tying up molecules in particulate form
Consist of volutin (polyphosphate), lipid, gllycogen, starch or sulfur
C. Intracytoplasmic Inclusions
Bacterial Anatomy
Internal Components
Single circular DNA chromosome (no nucleus)
Supercoiled DNA allows it to fit inside small bacterial cell
Irregularly shaped region in bacterial cytoplasm where circular DNA chromosome is located
Lacks a surrounding membrane
Contains:
- single, circular double-stranded DNA molecule
- proteins that help in DNA folding and regulation
D. Nucleoid
Bacterial Anatomy
Internal Components
Small, circular DNA molecules that
- carry extra genes (antibiotic resistance genes)
- can be transferred between bacteria through conjugation
- used in biotechnology (genetic engineering, cloning)
E. Plasmids
Bacterial Anatomy
Internal Components
name _ is suggestive of a spore or seed-like form (endo means within)
2-phase life cycle: _, _
F. Endospore
2 phase life cycle:
1. Vegetative cell - metabolically active
2. Endospore - when exposed to adverse envi conditions, capable of high resistance and very long term survival
Bacterial Anatomy
Internal Components
F. Endospores
Can remain dormant indefinitely (not reproductive) but germinate quickly when appropriate trigger is applied
Metabolically inactive
Stable for years
Endospores differ significantly from vegetative or normally functioning cells
Formed by gram + bacteria
Bacteria | Disease
Bacillus anthracis - anthrax
Clostridium botulinum - botulism
Clostridium perfringens - gas gangrene
Clostridium tetani - tetanus
Bacterial Anatomy
Internal Components
F. Endospores
Properties of Endospores
- Core - spore protoplast containing normal cell structures but is metabolically inactive
- Spore wall - innermost layer surrounding inner spore membrane, conntains normal peptidoglycan and becomes cell wall of germinating vegetative cell
- Cortex - thickest layer of spore envelope, cortex peptidoglycan is extremely sensitive to lysozyme and autolysis plays a role in spore germination
- Spore coat - cortex is enclosed by fairly thick spore coat
- Exosporium - some have additional rather loose covering which may have distinctive ridges and grooves
Spore - can survive adverse conditions for years
- Core - DNA, ribosomes, glycolytic enzymes
- Cytoplasmic Membrane
- Spore wall - normal peptidoglycan
- Cortex - thick layer of cross-linked peptidoglycan
- Keratin Spore Coat - protein
CCSCK
Bacterial Anatomy
Internal Components
E. Endospores
Shape and Position of Bacterial Spore
2 shapes: oval or spherical
3 positions: central, subterminal, terminal
2 bulges: bulging or nonbulging
FREE SPORE
Oval central nbg (oval middle)
Spherical central nbg (circle middle)
Oval subterminal nbg (oval near end)
Oval subterminal bg (oval near end bulged)
Oval terminal bg (oval end bulged)
Spherical terminal (circle end bulged)
FREE SPORE
Bacterial Anatomy
Internal Components
F. Endospores
Sporulation
- DNA is copied
- Spore septum forms
- Peptidoglycan layers develop
- Spore coat provides protection
- Endospore is released and remains dormant until conditions improve
Germination - return to vegetative growth
Bacterial Anatomy
Internal Components
F. Endospores
Dehydrated, metabolically inactive
Thick coat
Resistant to ordinary cleaning methods and boiling
Pressurized steam at 120 degrees C for 20-30 minutes will destroy spores
