Microbio rest of ch 4: Atypical cell walls, and eukaryotic cells

Atypical cell walls

• Acid-fast cell walls

  • Like gram-positive cell walls

    • But their cell wall contains mycolic acid 

  • Waxy lipid (mycolic acid) bound to peptidoglycan

    • Makes really thick coating 

  • Mycobacterium

    • Deadly pathogen

  • Nocardia

  • Stain with carbolfuchsin

Atypical cell walls, MYCOPLASMA

• Lack cell walls

• Sterols in plasma membrane

  • Bacteria cell walls usually dont have sterols, but this one is an exception 

Atypical cell walls, ARCHAEA

• Wall-less, or 

• Walls of pseudomurein (lack NAM and D-amino acids)

Damage to the cell wall

• Lysozyme hydrolyzes bonds in peptidoglycan

  • “Breaks the stick”

• Penicillin inhibits peptide bridges in peptidoglycan

  • “Breaks the rope”

• Protoplast is a wall-less gram-positive cell 

• Spheroplast is a wall-less gram-negative cell 

  • Protoplasts and spheroplasts are susceptible to osmotic lysis 

• L Forms are wall-less cells that swell into irregular shapes 

What is a protoplast?

wall-less gram-positive cell 

What is a spheroplast

wall-less gram-negative cell 

What are L-forms?

wall-less cells that swell into irregular shapes 

Protoplasts and spheroplasts are susceptible to

osmotic lysis

The plasma (cytoplasmic) membrane

• Phospholipid bilayer that encloses the cytoplasm

• Peripheral proteins on the membrane surface

• Integral and transmembrane proteins penetrate the membrane 

Prokaryotic cell membrane:

• Also called inner membrane

• Double phospolipid layer with proteins (ofter glygoproteins)

• Lipids differ from eukaryotic cell membranes

  • No sterols (ecxeption: Mycoplasma steal sterols from host)

• Protection towards outside

• Containment  of cytoplasmic material

• Allow for selective uptake of molecules (selective permeability) 

• Site of energy production in many species

  • Compensate for not have mitochondria by having mitochondria proteins on their plasma membrane

• Target of some antibiotics (e.g. polymxin B) and disinfectants (e.g. alcohols)

• Damage to the membrane by alcohols, quaternary ammonium (detergents), and polymyxin antibiotics causes leakage of cell contents

Structure of membrane

• Fluid mosaic model (very flexible)

  • Membrane is as viscous as olive oil 

  • Proteins move freely for various functions

  • Phospholipids rotate and move laterally 

  • Self-sealing

• The plasma membrane’s selective permeability allows the passage of some molecules, but not others

• Contain enzymes for ATP production

• Some membranes have photosynthetic pigments on foldings called chromatophores

Functions of cell membrane:

• Selective barrier (selectively permeable)

• Secrete exoenzymes

  • Amylases

  • Lipases

  • Peptidases

• ETS is located here 

  • ETS= Electron transport system

• Enzymes for cell wall synthesis

• If photosynthesis, enzymes are located on membranous structures called thylakoids

• Mesosomes- invaginantion of cell membrane attached to DNA

Functions of cell membrane:

• If photosynthesis, enzymes are located on membranous structures called

thylakoids

What are invaginantion of cell membrane attached to DNA

mesosomes

The movement of materials acoss membranes:

• Passive processes: substances move from high concentration to low concentration; no energy expended

• Active processes: substances move from low concentration to high concentration; energy expended

Passive processes:

substances move from high concentration to low concentration; no energy expended

active processes

substances move from low concentration to high concentration; energy expended

Prokaryokes-plasma membrane as a barrier 

• Osmosis: diffusion of water across a semi-permiable membrane. Environment surrounding cells may contain amounts of dissolved substances (solutes) that are….

  • Equal to

  • Less than

  • Greater than… those found within the cell 

• Tonocity and osmosis 

• Isotonic: equal concentration of a solurte inside and outside of cell

• Hypertonic: a higher concnentrartion of solute

  • Water from cell going out 

• Hypotonic: a lower concentration of a solute. Water will always move toward a hypertonic environment!!!!!

• Osmolysis leads to bursting of cell

What is the ..

• diffusion of water across a semi-permiable membrane. Environment surrounding cells may contain amounts of dissolved substances (solutes) that are….

  • Equal to

  • Less than

  • Greater than… those found within the cell 

osmosis

• a higher concnentrartion of solute

  • Water from cell going out 

hypertonic

equal concentration of a solurte inside and outside of cell

isotonic

a lower concentration of a solute. Water will always move toward a hypertonic environment!!!!!

hypotonic

Antimicrobial agents:

• Disinfectants and antiseptics

  • Many are aimed at disrupting the cell membrane

    • Ex: alcohols and detergents 

Prokaryotic cytoplasm:

• 80% water

• Contains primarily proteins (enzymes), carbohydrates, lipids, inorganic ions, many low molecular weigh compounds

• Thick, aqueous, semitransparent, and elastic

Prokaryotic Nucleiod:

• Bacterial chromosomes

• Constains the essential genetic material

• Circular double-stranded DNA stabilized by histone-like proteins (not by histones)

• No nuclear envelope

• Cell division by binary fission 

Prokaryotic plasmids:

• Small circular double-stranded DNA that can multiply DNA that can multiply independently 

• Non essential under normal physiological conditions

  • Cell can survive without plasmid 

• Contain additional genes ofter involved in pathogenesis

  • Virulence factors

  • Antibiotic resistance

  • Toxic metal resistance

• Copy number varies (a few hundreds)

  • Can be exploited for recombinant protein production

Prokaryotic ribosomes:

• Not all bacterial cells have plasmids 

Prokaryotic ribosomes:

• 70s ribosomes (30s + 50s subunit)

  • S= Sverdberg unit (sedimentation rate upon centrifugation)

  • Smaller than eutkaryotic ribosome

  • Sediment differently

• Consist of proteins and ribosomal RNA

• Site of protein synthesis 

• Contain 16S rRNA on 30s subunit 

  • 16S is important for the classification and identification

Selective toxicity:

• Some antibiotics are aimed at the 70 S ribosomes of bacterial cells

• Streptomycin, Neomycin, Erythromycin, and tetracyline work by inhibiting protein sytthesis by disrupting the 70s ribosome 

inclusions:

• Metachromatic granules (volutin)- phosphate reserves

• Polysaccharide granules- energy reserves

• Lipid inclusions- energy resevrs

• Sulfur granules- energy reserves

• Cabroxysomes- RuBis _COenzyme for _CO2 fixation during photosynthesis 

• Gas vacuoles- protein covered cylinders that maintain buoyancy

• Magnetosomes- irone oxide inclusions; destroy _H2o2

Bacteiral Endospores: Unique endurance forms

• Sporulation is a complex process

• Triggered under unfavorabele conditions

  • Not having enough nutrients, water, etc

• Very low water content

• Spore is multilayered 

• Resistance through spore coat(protein layer)

• Can survive through thousands of years

• Germination is triggered under favorable conditions

• Clostridium sp., Bacillus sp.

Endospores

formed under periods of environmental stress

• Only found in gram (+) bacteria

• Bacillius

  • Bacillius cerus (grows on rice crop, not deadly )

  • Bacillus anthracis (deadly)

• Clostridium

  • Clostridium tetani

  • Clostridium botulinum

  • Clostridium perfringens (causes gas gangrene)

    • Terminal 

    • Subterminal 

    • Central 

Endospores,

• Bacillius

• Bacillius cerus (grows on rice crop, not deadly )

• Bacillus anthracis (deadly)

Endospores :

Clostridium

• Clostridium tetani

• Clostridium botulinum

• Clostridium perfringens(causes gas gangrene)

  • Terminal 

  • Subterminal 

  • Central

Eukaryotic cell structure:

• Eukaryotic structure in plant and animal cells:

  • Peroxisome

  • Nucleus

  • Nucleolus

  • Rough endoplasmic recticulum

  • Smooth endoplasmic reticulum

  • Microtubule

  • Microfilament

  • Mitochondrion

  • Plasma membrane

  • Ribosome

• Eukaryotic structure in animal cell only

  • Centrisome

  • Centriole

  • Pericentoral material

  • Lysosome

  • Basal body

  • Flagellum 

• Eukaryotic structure in plant cell only

  • Vacuole 

  • Cell wall

  • chloroplast

Eukaryotic structure in plant and animal cells:

• Peroxisome

• Nucleus

• Nucleolus

• Rough endoplasmic recticulum

• Smooth endoplasmic reticulum

• Microtubule

• Microfilament

• Mitochondrion

• Plasma membrane

• Ribosome

Eukaryotic structure in animal cell only

• Centrisome

• Centriole

• Pericentoral material

• Lysosome

• Basal body

• Flagellum 

Eukaryotic structure in plant cell only

• Vacuole 

• Cell wall

• chloroplast

Flagella and cilia, eukaryotes

• Projections used for locomotion or moving substances along the cell surface 

• Flagella- long projections; few in number

  • Flagella in eukaryotes move like a whip 

  • Men have flagella in sperm, women have no flagella 

• Cilia- short projections; numerous 

What are long projections; few in number

• in eukayotes they move like a whip 

• Men have flagella in sperm, women have no flagella 

flagella

What are short projections; numerous

cilia

Flagella and cilia both consist of:

• Microtubules made of the protein tubulin

• Microtubules are organized as 9 pairs in a ring, plus 2 microtubules in the center (9 + 2 array)

• Allow flagella to move in a wavelike manner 

The cell wall and glycocalyx, eukaryotes:

• Cell wall

  • Found in plants, algae, and fungi

  • Made of carbohydrates (cellulose– plants, chitin— fungi, glucan and mannnan–yeasts)

• Glycoclyx:

  • Carbohydrates bonded to proteins and lipids in the plasma membrane

  • Found in animal cells

Cell wall of eukaryotic cell

• Found in plants, algae, and fungi

• Made of carbohydrates (cellulose– plants, chitin— fungi, glucan and mannnan–yeasts)

Glycoclyx:

• Carbohydrates bonded to proteins and lipids in the plasma membrane

• Found in animal cells

The plasma (cytoplasmic) membrane

• Similar in structure to prokaryotic cell membranes 

  • Phospholipid bilayer

  • Integral and peripheral proteins

• Differences in structure 

  • Sterols—complex lipids

  • Carbohydrates— for attachment and cell-to-cell recognition

The plasma (cytoplasmic) membrane

• Differences in function

  • Endocytosis- phagocytosis and pinocytosis

  • Phagocytosis: pseudopods extend and england particles

    • Happens in presence of pathogens 

  • pinocytosis : membrane folds inward, bringing in fluid and dissolved substances 

What is endocytosis?

phagocytosis and pinocytosis

What is phagocytosis?

pseudopods extend and engulf particles

• Happens in presence of pathogens 

What is pinocytosis ?

membrane folds inward, bringing in fluid and dissolved substances 

Cytoplasm:

• Cytoplasm: substance inside the plasma and outside the nucleus

• Cytosol: fluid in portion of cytoplasm

• Cytoskeleton: made of microfilaments and intermediate filaments; gives shape and support

• Cytoplasmic streaming: movement of the cytoplasm throughout a cell

What is the substance inside the plasma and outside the nucleus

cytoplasm

What is the fluid in portion of cytoplasm

Cytosol

What is made of microfilaments and intermediate filaments; gives shape and support

cytoskeleton

What is the movement of the cytoplasm throughout a cell

Cytoplasmic streaming

Ribosomes

• Sites of protein synthesis

• 80s

  • Consists of the large 60s and the small 40s subunit

  • Membrane-bound: attached to endoplasmic reticulum

  • Free: in cytoplasm

  • Can be bound or stuck on endoplasmic reticulum

• 70s 

  • In chlorplasts and mitochondria 

  • Made of of 30 and 50

80 S ribosomes

• Consists of the large 60s and the small 40s subunit

• Membrane-bound: attached to endoplasmic reticulum

• Free: in cytoplasm

• Can be bound or stuck on endoplasmic reticulum

• Contain 18S RNA subunit 

  • Important for identification

70 S ribosomes

• In chlorplasts and mitochondria 

• Made of of 30 and 50

The nucleus

• Double membrane structure (nucleus envelope) that contains the cells DNA

• DNA is complexed with histone proteins to form chromatin

• During mitosis and meiosis, chromatin condenses into chromosomes 

Endoplasmic reticulum:

• Folded transport network

• Rough ER: studded with ribosomes; sites of protein synthesis

• Smooth ER: no ribosomes; synthesizes cell membranes, fats, and hormones 

Identify this as ROUGH ER or SMOOTH ER:

• studded with ribosomes; sites of protein synthesis

rough ER

Identify this as ROUGH ER or SMOOTH ER:

• no ribosomes; synthesizes cell membranes, fats, and hormones 

smooth ER

Golgi complex:

• Transport organelle

• Modifies proteins from the ER

• Transports modified proteins via secretory vesicles to the plasma membrane 

Organelles:

• Lysosomes

  • Vesicles formed in the golgi apparatus

  • Contains digestive enzymes

• Vacuoles

  • Cavities in the cell formed from the golgi complex

  • Bring food into cells; provide shape and storage

What are lysosomes?

• Vesicles formed in the golgi apparatus

• Contains digestive enzymes

What are vacuoles?

• Cavities in the cell formed from the golgi complex

• Bring food into cells; provide shape and storage 

Mitochondria

• Double membrane

• Contain inner folds (cristae) and fluid matrixx

  • Folded increases surface area

• Involved in cellular respiration (ATP production)\

• 70 S ribosomes

• Circular chromosomes

• Replicate on their own 

Chloroplats:

• Locations of photosynthesis 

• Contain flattened membranes (tylakoids) that contain chlorophyll

• 70 S ribosomes

• Circular chromosomes

• Replicate on their own

Organelles,

• Peroxisomes:

• Oxidises fatty acids; detroy H2O

• Centrosomes

  • Networks of protein fibers and centrioles

  • Form the mitotic spindle; critical role in cell division

Evolution of eukaryotes:

• Life arose as simple organisms 3.5 to 4 billion years ago 

• First eukaryotes evolved 2.5 billion years ago

• Endosymbiotic theory

  • Larger bacterial cells engulfed smaller bacterial cells, developing the first eukaryotes

  • Ingested photosyntetic bacteria became chloroplasts 

    • Ingested aerobic bacteria became mitochondria

Model of the origin of eukaryotes

• LUCA:

  • Last universal common ancestor