gram -

osmosis:
​diffusion of water (movement of water from an area of high concentration to an area of low concentration)  across a selective membrane

 A capsule and slime layer together are called a glycocalyx.

lopho = tuft

                  the outer membrane of gram-negative                                 bacteria serves as an extra barrier which:
 *resists certain antimicrobial chemicals
 *makes it harder to inhibit or kill than gram + bacteria

Pili, which are longer and more rigid than fimbriae, are used for locomotion, to attach to surfaces, and to help with gene transfer. 

                                questions to consider
 1. Explain why all cells don't exhibit the same structure. 
 2. What is the one main distinction between prokaryotic and eukaryotic cells?
 4. List the 4 cell structures seen in all bacterial cells and a function for each. 
 5. Bacterial cells walls are made out of a unique polysaccharide called ________________.
​ 6. Cell membranes are composed of molecules called __________________.
      Describe the structure of this molecule.
      How are these molecules arranged in the cell membrane?
      What characteristics of these molecules produce this membrane arrangement?
​ 7. Define diffusion.
     Define osmosis.
 8. There are four categories of membrane proteins. Describe the function of one category.
 9. What is the function of:
          plasmids?
          endospores?
 10. Bacteria reproduce asexually via a process called _______________________.

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     each phospholipid has:
1. phosphate group head which
       is hydrophilic (H2O loving)
2. two fatty acid tails which are  
       hydrophobic (water hating)

What might  the membrane of a microbe living in cold climates look like vs one adapted for a hot climate?

nucleoid =
non-membrane bound region where prokaryotic DNA is located. bacterial DNA is structured as a single chromosome. the nucleoid also exhibits various proteins and RNAs. 

we can use plasmids as tools to clone, transfer, and manipulate genes. We call these plasmids recombinant plasmids or vectors. engineered vectors can be inserted into bacteria via a process called
transformation. When bacteria divide, they copy these plasmids and so also copy the DNA inserted into them line a DNA factory. 

 gram - bacteria have a cell wall with a thin peptidoglycan layer surrounded by an outer membrane. this outer membrane is embedded with lipopolysaccharide (LPS) which is toxic to animals. there's also a space between the membranes called the periplasmic space which is filled a jellyish fluid that helps neutralize potentially toxic substances. 

​This technique identifyies the bacteria that causes TB and leprosy 
(Mycobacterium tuberculosis and Mycobacterium leprae). 

Most are between 0.5 and 2.0𝜇m

bacteria get their nutrients into their cells via diffusion. Teeny cells have a high surface area-to-volume ratio which permits diffusion into the very center of the cell. 

chloroplasts and mitochondria found in eukaryotic cells contain  their own ribosomes which supports the
endosymbiotic theory

bur first...how does water enter/exit the cell?

capsule        slime layer      biofilm

Acid Fast Staining also permits identification
of bacterial cells based on cell wall structure

      extracellular structures:

 1. flagella   2.  fimbrae   3. pili​

Aspartate is a nitrogen source necessary for the synthesis of amino acids, nucleotides, and amino sugars by bacteria.  

mono - one

Bacterial cells walls are made from
peptidoglycan.
Peptidoglycan isnt found anywhere else on Earth.

identifying bacterial shapes and arrangements permits us to 
identify pathogens. Sometimes, bacteria is pleiomorphic...it can change its shape and arrangement to enhance its ability to survive when conditions change.

​this permits bacteria to form biofilms, those sticky communities teeming with one or more species of bacteria. biofilms permit  microbes to communicate and respond as one entity, hence increasing the cells' survival. bacteria use their fimbriae to stick to a surface then secrete a sticky protective matrix. This continues resulting in a bacterial apartment building. 












​here's a biofilm from your teeth...floss!!!

​







​

and here's the pleiomorphic bacteria Helicobacter pylori which causes ulcers.

why don't all cells have the same structure?

  flagella propel bacteria by spinning 
like a rotary propeller from a crank shaft like structure called a basal body embedded in the cell wall.

gram -

let's examine the structure of prokaryotic cells from the outside in...

and why are bacterial cells
​soooo tenny?

peptidoglycan is a polysaccharide made from two cousins of glucose
N-acetylglucosamine (NAG) and
 N-acetylmuramic acid (NAM).
These sugars are arranged in alternating long chains cross-linked
in a lattice-like structure.

bacteria reproduce asexually via
by binary fission. 

 spore-forming prokaryotes that cause harm clinically are
in the Gram + Bacillus, Clostridium, and Clostridioides genera. 
Very dangerous bacteria such as 
Clostridium tetani, C. botulinum and C. difficile





​
​
can survive on surfaces despite care taken to clean them. 

Bacillus anthracis spores have been bioweaponized. When the spores are inhaled, they germinate into vegetative cells and cause serious infection.

acid-fast staining technique detects mycolic acid, a waxy fat, in bacterial cell walls. Bacteria possessing this waxy layer appear pinkish after the procedure.

plasmids =
small, circular DNA strand separate a cell's chromosomal DNA. the genes carried in plasmids are often associated with advantages such as antibiotic resistance. Bacteria can transfer plasmids to one another through a process called conjugation.

fimbriae 

speaking of cell division...

chapter 3: prokaryotic cells

Fimbriae are short, bristly bits of protein that cover the surface of some bacteria. fimbriae help prokaryotes stick to a surface, to another cell, or to each other when creating biofilms. Certain Salmonella and E. coli used their fimbriae to infect cells.

proteins are embedded in the phospholipid bilayer membrane

more about the cell wall

can bacterial cells hibernate?

 an example of a
bacterial membrane receptor protein
​ is the "Tar" protein found on E coli surfaces. An aspartate receptor, the TAR receptor allows the cell to detect and move towards an aspartate chemical gradient via chemotaxis.

cytoplasm =
the jelly ish fluid inside a bacterial cell.
​In the cytoplasm you'll find ribosomes,
DNA in the nucleoid,
plasmids, nutrients and
enzymes. this is where
most of the cell's metabolic processes occur.

 proteins embedded in the plasma membrane can make up half of its mass. 
​membrane proteins can be:
1. transport proteins
2. receptor proteins
3.  adhesion proteins
4. enzymatic proteins.              

now, let's look inside the cell...

Bacteria are divided into two major groups: 
Gram positive and Gram negative
(based on their reaction to Gram staining, an identifying technique named after Danish scientist Hans Gram 1853–1938).








​

Gram +  vs  Gram - 
bacterial responses to the staining procedure are due difference in their cell wall structure. 

this process proceeds in 5 steps.
the frequency any given species undergoes binary fission differs.

 this phospholipid bilayer is fluid...
warmer temps and unsaturated fatty acids increase this  fluidity while colder temps and saturated fatty acids decrease fluidity.

Biofilmsare communities of microbes stuck together and adhered to a surface encased in a slimy layer.

cell structure matches cell function.
​a muscle cell has a very different structure AND function ​vs a nerve cell.
a plant cell differs significantly from a bacterial cell.  

cell surface identity marker proteins are also called antigens. bacterial antigens are molecules on the surface of bacteria that can trigger an immune response. They can be found on the cell wall or flagella. 

there are also transport proteins...

 membrane proteins
  can be attached to lipids or carbohydrates and are therefore called either lipoproteins or glycoproteins.  

plasmolysis

 Cells may also exhibit a 
    slime layer
 similar to a capsule but
loosely associated to the cell surface so easily washed away.

flagella:
seen on half of all bacterial species

cytoskeleton:
these protein filaments provide the cell structure, support, direct cell division and assist in building cells walls.

so although some molecules can diffuse directly across the membrane.
other molecules rely on
​membrane transport proteins. 

ribosomes:
organelles where amino acids are bonded together to make proteins using RNA for  instructions relayed from the cell's DNA. Bacterial ribosomes are a bit smaller than eukaryotic ribosomes. Research is trying to exploit this difference when creating new antibiotics.
bacterial ribosomes are composed of two subunits: called 50S and 30S. 

in simplistic terms, the S stands for sedimentation rate

inclusion bodies:
​concentrations of molecules such as:
 
stored glycogen used for food

stored poly-𝛽-hydroxybutyrate (PHB) to serve as an energy reservoir when sugar reserves are low

carboxysomes which are used by cyanobacteria "fix" carbon

magnetosomes which contain  magnetic iron which  helps some bacteria to dive deep in water where its low O2
​

transport proteins may be...

endospores:
sometimes vegetative cells ​(active and alive cells)
are stressed out and produce spores which permit some bacterial species to lay in a dormant state. these spores resist environmental pressures such as cold, heat, desiccation, radiation, chemical contamination etc.

really old spores (>1/4 million YO) have been grown in culture!
bacterial spores are able to regerminate into vegetative cells.

this isn't considered cell division...
just cell preservation. 

periplasmic flagella are found in the periplasmic space of some Gram -
bacteria and allow spirochetes to move in a corkscrew fashion. 

amphi = both

these questions have been updated in preparation for our first assessment Monday 2/10

Gram staining allows us to classify bacterial cells based on cell wall structure

a bilayer of phospholipids

trichous = hairlike

 Alcohol dissolves lipids in the outer membrane damaging the cell so
alcohol swabs can be used to cleanse the skin clinically

gram +

the proteins along with the
phospholipid bilayer is described as
the fluid mosaic model

pili

ATP, fueling active transport, is the energy ​currency of cells

there are two primary categories of cells:
prokaryotic and eukaryotic

bacteria can move through fluid  50 times its length in one second which is like YOU running ​204 mph!

 the cell membrane

back to shapes and arrangements 

                The exterior of Bacteria is different from                            that of the Archaeans and Eukaryotes.
 Cell walls function as a structural, protective layer.
                  Some bacteria also have:
    1. A polysaccharide capsule found outside the cell
        wall which:
        *helps the cell attach to surfaces, 
        *protects the cell from dehydration,
​        *protects the cell from toxins
        *helps prevent the cell from being attacked
                 by phagocytes thereby helping bacterial
                 pathogens resist our immune system.
    2. Flagella which is used for locomotion
    3. Pili (pilus/fimbriae) used to attach to surfaces
    4. Plasmids which are ciruclar strands of DNA                           separate from the singular chromosome
    5. Endospores which can resist environmental
                 extremes

diffusion:

movement of substances from an area of high concentration to an area of low concentration

     the phospholipids are arranged in a bilayer

peri = all around

​Prokaryotic and eukaryotic cells differ significantly in structure,
             however, all cells have four common structures:
 1.a plasma membrane
 2. cytoplasm
 3. nucleic acids
 4. ribosomes

3 systems:
hypertonic    isotonic     hypotonic

gram + bacterial cell walls also contain 
teichoic and lipoteichoic acids
​embedded within the peptidoglycan layers
adds strength to the cell wall and contributes to an acidic charge on the cell surface.

concentration gradient =
the difference in the concentration of a molecule  between two areas

phospholipid =
polymer made from
1 glycerol
2 fatty acids
​1 phosphate group

gram +

but the treatment of infections caused by gram-negative bacteria
requires drugs that can cross the outer membrane

solution =
solute + solvent

made from a protein called flagellin