Chapter
Prokaryotic Microorganisms: Bacteria
Cell shape and arrangement (Fig. 4.22)
Prokaryotic cell structure (Fig. 4.1)
1. Cell wall 2. Cell membrane 3. Periplasmic space 4. Cytoplasm 5. Internal structures 6. External structures
1. Cell wall
2. Cell membrane
3. Periplasmic space
4. Cytoplasm
5. Internal structures
6. External structures
Why are the details of prokaryotic cells important to MICR 201 students?
They are much different from our cells which are eukaryotic. The differences can be exploited as targets for antimicrobial agents to control bacteria (e.g. to treat and prevent diseases) without harming our cells. In addition, some of the components are virulence factors that enable bacterial pathogens to establish an infection and cause disease. You will learn more about these aspects of microbiology in the second half of the semester.
1. Prokaryotic cell wall
Cell wall composition and structure (Fig. 4.15 and 4.16)
Gram positive bacteria
o Peptidoglycan (Fig. 4.14) o Teichoic acids Ex. Bacillus anthracis
o Peptidoglycan (Fig. 4.14)
o Teichoic acids
Ex. Bacillus anthracis
Gram negative bacteria
o Peptidoglycan o Outer membrane (Fig. 4.16) -Phospholipids -Lipopolysaccharide (a.k.a. endotoxin) -Proteins (Ex. porins) Ex. Eshcerichia coli
o Peptidoglycan
o Outer membrane (Fig. 4.16)
-Phospholipids -Lipopolysaccharide (a.k.a. endotoxin) -Proteins (Ex. porins)
-Phospholipids
-Lipopolysaccharide (a.k.a. endotoxin)
-Proteins (Ex. porins)
Ex. Eshcerichia coli
Acid fast bacteria
o Peptidoglycan o Waxy lipids (mycolic acids) Ex. Mycobacterium tuberculosis
o Waxy lipids (mycolic acids)
Ex. Mycobacterium tuberculosis
Mycloplasmas
o Do not have a cell wall Ex. Mycoplasma pneumoniae
o Do not have a cell wall
Ex. Mycoplasma pneumoniae
Peptidoglycan
o Polymer of N-acetylglucosamine + N-acetylmuramic acid (carbohydrates) (Fig. 4.14) o Cross-linked by short peptides (amino acids)
o Polymer of N-acetylglucosamine + N-acetylmuramic acid (carbohydrates) (Fig. 4.14)
o Cross-linked by short peptides (amino acids)
Teichoic acids
Only present in gram positive cell walls Acidic polysaccharides (glycerol or ribitol linked by phosphate) Give the cell wall a negative charge
Only present in gram positive cell walls
Acidic polysaccharides (glycerol or ribitol linked by phosphate)
Give the cell wall a negative charge
Ex.
Outer membrane (only in gram negative cell walls)
Bilayer composed of: Phospholipid (like that of the cell membrane) Lipopolysaccharide (lipid + polysaccharides) Proteins called porins that form pores in the membrane Outside of the cell
Bilayer composed of:
Phospholipid (like that of the cell membrane)
Lipopolysaccharide (lipid + polysaccharides)
Proteins called porins that form pores in the membrane
Outside of the cell
Effects of cell wall on staining
Cell wall affects ability to be stained by Gram and acid-fast stains
Gram positive bacteria have a thick peptidoglycan layer, no outer membrane
Not decolorized by alcohol (crystal violet dye is retained) Ex. Clostridium botulinum
Not decolorized by alcohol (crystal violet dye is retained)
Ex. Clostridium botulinum
Gram negative bacteria have a thin peptidoglycan layer plus an outer membrane
Decolorized by alcohol (crystal violet is removed) Counterstained with safranin Ex. Escherichia coli
Decolorized by alcohol (crystal violet is removed)
Counterstained with safranin
Ex. Escherichia coli
Acid-fast bacteria have a thin peptidoglycan layer plus a thick layer of lipids and waxes (mycolic acids) that block entry of dyes
The cells must be stained with steaming carbolfuschin which penetrates the lipid layer Not decolorized by acid-alcohol (carbolfuchsin dye is retained) Ex. Mycobacterium tuberculosis
The cells must be stained with steaming carbolfuschin which penetrates the lipid layer
Not decolorized by acid-alcohol (carbolfuchsin dye is retained)
2. Cell membrane (See Chapter 2, page 45)
Bilayer of:
1) Phospholipids 2) Proteins o Imbedded in or on membrane surfaces o Transport substances across the membrane Ex. nutrients, metabolic wastes and toxins o Transmit signals of environmental conditions to interior Ex. presence of nutrients o Synthesize ATP -Main source of energy for cell
1) Phospholipids
2) Proteins
o Imbedded in or on membrane surfaces o Transport substances across the membrane Ex. nutrients, metabolic wastes and toxins o Transmit signals of environmental conditions to interior Ex. presence of nutrients o Synthesize ATP -Main source of energy for cell
o Imbedded in or on membrane surfaces
o Transport substances across the membrane
Ex. nutrients, metabolic wastes and toxins
o Transmit signals of environmental conditions to interior
Ex. presence of nutrients
o Synthesize ATP
-Main source of energy for cell
Contains: o Proteins that help transport substances into the cell o Enzymes that begin process of food digestion and protect the cell from invasion by viruses
Contains:
o Proteins that help transport substances into the cell o Enzymes that begin process of food digestion and protect the cell from invasion by viruses
o Proteins that help transport substances into the cell
o Enzymes that begin process of food digestion and protect the cell from invasion by viruses
80% Water 20% Dissolved or suspended substances o Proteins (enzymes, etc.) o Carbohydrates o Organic acids o Nucleotides Ex. ATP o Nucleic acids (DNA and RNA) o Inorganic ions Ex. K+, Na+, Cl-, HPO4=, NH4+, Mg++ , Ca++
80% Water 20% Dissolved or suspended substances
o Proteins (enzymes, etc.) o Carbohydrates o Organic acids o Nucleotides Ex. ATP o Nucleic acids (DNA and RNA) o Inorganic ions Ex. K+, Na+, Cl-, HPO4=, NH4+, Mg++ , Ca++
o Proteins (enzymes, etc.)
o Carbohydrates
o Organic acids
o Nucleotides
Ex. ATP
o Nucleic acids (DNA and RNA)
o Inorganic ions
Ex. K+, Na+, Cl-, HPO4=, NH4+, Mg++ , Ca++
Present in all bacteria
-Ribosomes. Site where proteins are synthesized (Fig. 4.19) Two subunits containing RNA and protein -Chromosome (DNA)
-Ribosomes. Site where proteins are synthesized (Fig. 4.19)
Two subunits containing RNA and protein
-Chromosome (DNA)
Present in some bacteria
Inclusions: Polymers that store carbon, energy and nutrients (Fig. 4.20) Ex. polyphosphate, polyhydroxybutyrate, sulfur Gas-filled vacuoles used by aquatic bacteria for flotation Internal membranes Ex. Sites of special metabolic reactions (such as photosynthesis or oxidation of methane) Endospore Resting stage of cell (metabolically inactive) (Fig. 4.21, Table 4.2)
Inclusions: Polymers that store carbon, energy and nutrients (Fig. 4.20)
Ex. polyphosphate, polyhydroxybutyrate, sulfur
Gas-filled vacuoles used by aquatic bacteria for flotation
Internal membranes
Ex. Sites of special metabolic reactions (such as photosynthesis or oxidation of methane)
Endospore Resting stage of cell (metabolically inactive) (Fig. 4.21, Table 4.2)
o Technically not an internal structure of the cell, but may be seen inside cells before the cell lyses May be thought of as a cell within a cell o Contains the chromosome (DNA) and ribosomes surrounded by thick protective layers of peptidoglycan and protein o Forms inside cell when conditions are unfavorable for growth Ex. Lack of moisture or nutrients o Helps cell survive harsh conditions Ex. Heat, toxic chemicals, drying o Germinates and becomes an active vegetative cell when conditions are favorable o Species of Bacillus and Clostridium are the main endspore formers Ex. Bacillus anthracis and Clostridium tetani endospores aid survival in dry soil Clostridium botulinum enodspores may survive heat during canning of food
o Technically not an internal structure of the cell, but may be seen inside cells before the cell lyses
May be thought of as a cell within a cell
o Contains the chromosome (DNA) and ribosomes surrounded by thick protective layers of peptidoglycan and protein
o Forms inside cell when conditions are unfavorable for growth
Ex. Lack of moisture or nutrients
o Helps cell survive harsh conditions
Ex. Heat, toxic chemicals, drying
o Germinates and becomes an active vegetative cell when conditions are favorable
o Species of Bacillus and Clostridium are the main endspore formers
Ex. Bacillus anthracis and Clostridium tetani endospores aid survival in dry soil Clostridium botulinum enodspores may survive heat during canning of food
Ex. Bacillus anthracis and Clostridium tetani endospores aid survival in dry soil
Clostridium botulinum enodspores may survive heat during canning of food
Flagellum Long, whip-like; for motility (Fig. 4.3) o One or more may be present at ends or all over surface of cell o Allow cells to move towards or away from environmental stimuli (nutrients, light, oxygen, toxic chemicals)
Flagellum Long, whip-like; for motility (Fig. 4.3)
o One or more may be present at ends or all over surface of cell o Allow cells to move towards or away from environmental stimuli (nutrients, light, oxygen, toxic chemicals)
o One or more may be present at ends or all over surface of cell
o Allow cells to move towards or away from environmental stimuli (nutrients, light, oxygen, toxic chemicals)
Pilus Hollow projections. 2 types o Conjugation pilus: transfer of DNA between cells (Fig. 4.9) o Fimbriae :adherence to surfaces (Fig. 4.8) Important for some pathogens
Pilus Hollow projections. 2 types
o Conjugation pilus: transfer of DNA between cells (Fig. 4.9) o Fimbriae :adherence to surfaces (Fig. 4.8) Important for some pathogens
o Conjugation pilus: transfer of DNA between cells (Fig. 4.9)
o Fimbriae :adherence to surfaces (Fig. 4.8)
Important for some pathogens
Capsule Gel layer surrounding cells (polysaccharide or polypeptide) (Fig. 4.11) o Protects some pathogens from immune system
Capsule Gel layer surrounding cells (polysaccharide or polypeptide) (Fig. 4.11)
o Protects some pathogens from immune system
Slime layer Thinner than capsule (Fig. 4.11) o Attaches cells to surfaces Ex. formation of biofilms on rocks in a stream, teeth, catheters, artificial joints o Concentrates nutrients near cell surface so that it can be taken into cell
Slime layer Thinner than capsule (Fig. 4.11)
o Attaches cells to surfaces Ex. formation of biofilms on rocks in a stream, teeth, catheters, artificial joints o Concentrates nutrients near cell surface so that it can be taken into cell
o Attaches cells to surfaces
Ex. formation of biofilms on rocks in a stream, teeth, catheters, artificial joints
o Concentrates nutrients near cell surface so that it can be taken into cell
Taxonomy
The science of classification.
Linnaeus introduced a system of taxonomy, called binomial nomenclature, for living organisms
o Each organism is given 2 names
1. First name: Genus
2. Second name: specific epithet
Together the Genus name and specific epithet = species name of a unique organism
Related organisms or organisms with similar characteristics are grouped together and have the same genus name
Ex. Escherichia coli Gram negative, non-sporeforming, rods Escherichia blattae Bacillus anthracis Gram positive, spore-forming rods Bacillus popillae
Escherichia coli Gram negative, non-sporeforming, rods Escherichia blattae
Bacillus anthracis Gram positive, spore-forming rods
Bacillus popillae
Species names are italized or underlined
Staphylococcus aureus or Staphylococcus aureus
Species names often give information about the organism
Greek and Latin terms are often part of name
Ex. Staphylococcus aureus Staphylo (Gk.) = cluster coccus (L.) = berry aureus (L.) = golden Cells are cocci arranged as clusters and colonies on solid growth medium are yellow Streptococcus bovis Strepto (Gk.) = chain bovis (L.) = cow Cocci, chains, lives in cow rumen Escherichia coli Named after Theodor Escherich Lives in the colon
Staphylococcus aureus Staphylo (Gk.) = cluster coccus (L.) = berry aureus (L.) = golden
Cells are cocci arranged as clusters and colonies on solid growth medium are yellow
Streptococcus bovis Strepto (Gk.) = chain bovis (L.) = cow
Cocci, chains, lives in cow rumen
Escherichia coli Named after Theodor Escherich
Lives in the colon
Thermus aquaticus Thermophilic (heat-loving) Lives in hot springs (and hot water heaters)
Thermus aquaticus Thermophilic (heat-loving)
Lives in hot springs (and hot water heaters)
Five-kingdom classification system for cellular organisms
Prokaryotes
1. Monera --Bacteria only
Eukaryotes
2. Protista --Algae and protozoa
3. Fungi --Yeast and molds
4. Plantae --Green plants
5. Animalia --Animals
-Helminths (worms) -Arthopods (ticks and mosquitoes)
-Helminths (worms)
-Arthopods (ticks and mosquitoes)
Viruses are acellular and not classified with cellular organisms
Characteristics used to classify bacteria
1. Morphology
Size, shape, external structures (pili, flagella, capsules) Endospores: presence or absence, location in cell
Size, shape, external structures (pili, flagella, capsules)
Endospores: presence or absence, location in cell
2. Staining
Gram positive, Gram negative, acid-fast
3. Nutrition
Carbon and energy sources, nitrogen sources Special requirements (Ex. vitamins, blood)
Carbon and energy sources, nitrogen sources
Special requirements (Ex. vitamins, blood)
4. Physiology
Aerobic, anaerobic, pH and temp. preferences Salt tolerance or requirement
5. Biochemistry
Presence of specific enzymes Ex. catalase: 2 H2O2 ---> O2 + 2 H2O
Presence of specific enzymes
Ex. catalase: 2 H2O2 ---> O2 + 2 H2O
6. Genetics
Sequences of DNA bases (A, T, G, C) Closely related species have DNA with similar sequences
Sequences of DNA bases (A, T, G, C)
Closely related species have DNA with similar sequences
Bergey's Manual
Sections of Bergy's Manual containing medically important bacteria
Section 1. Spirochetes: Gram negative, corkscrew shaped
Treponema Syphilis, gum disease Borrelia Lyme disease
Treponema Syphilis, gum disease
Borrelia Lyme disease
Section 2. Helical: Gram negative
Campylobacter Abortions in cattle. food poisoning Helicobacter Stomach ulcers
Campylobacter Abortions in cattle. food poisoning
Helicobacter Stomach ulcers
Section 4. Gram-negative aerobic rods and cocci
Pseudomonas Usually not pathogenic Causes opportunistic infections Ex. following severe burns
Pseudomonas Usually not pathogenic
Causes opportunistic infections
Ex. following severe burns
Neisseria Gonorrhea, meningitis (inflammation of the membrane covering the brain and spinal cord)
Brucella Brucellosis in humans Abortions in cattle, swine and dogs
Brucella Brucellosis in humans
Abortions in cattle, swine and dogs
Section 5. Facultatively anaerobic Gram negative rods
Escherichia Enteritis (inflamation of small intestine) Salmonella Enteritis Yersinia Bubonic plague Vibrio Cholera (acute enteritis causing massive fluid loss and shock)
Escherichia Enteritis (inflamation of small intestine)
Salmonella Enteritis
Yersinia Bubonic plague
Vibrio Cholera (acute enteritis causing massive fluid loss and shock)
Section 8. Anaerobic Gram negative cocci
Veillonella Tooth abscesses and gum disease
Section 9. Obligate intracellular parasites
Rickettsia Rocky Mtn. spotted fever Chlamydia Eye infections, pneumonia
Rickettsia Rocky Mtn. spotted fever
Chlamydia Eye infections, pneumonia
Section 10. Mycoplasmas Lack cell walls, shape is pleomorphic
Mycoplasma Atypical pneumonia
Section 12. Gram positive cocci
Streptococcus Strep throat Staphylococcus Skin abscesses
Streptococcus Strep throat
Staphylococcus Skin abscesses
Section 13. Endospore-forming Gram positive rods and cocci
Bacillus Anthrax: cattle, sheep and humans Clostridium Tetanus, food posioning (botulism)
Bacillus Anthrax: cattle, sheep and humans
Clostridium Tetanus, food posioning (botulism)
Section 14. Nonsporing Gram positive rods
Listeria Meningitis
Section 15. Nonsporing Gram positive irregular rods
Corynebacterium (club shaped) Diptheria Actinomyces (branched filaments) Jaw abscesses
Corynebacterium (club shaped) Diptheria
Actinomyces (branched filaments) Jaw abscesses
Section 16. Mycobacteria (Acid fast)
Mycobacterium Tuberculosis, leprosy
Section 29. Streptomycetes Gram positive, filamentous, spore-forming
No pathogens, produce antibiotics used to treat infections Streptomyces Produces streptomycin
No pathogens, produce antibiotics used to treat infections
Streptomyces Produces streptomycin
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SIUC / College of Science / Microbiology / Microbiology 201 http://www.micro.siu.edu/micr201/chapter 4N.html Last updated: Feb. 1, 2007 /jdh