Microbio Chapter 3

to survive drying and extremely cold environments, the ability to create endospores in environments of high stress would be necessary, the cell would also need to have external fimbriae, which are short, bristle-like structures that extrude from the cell surface and exhibit adhesive properties that help prokaryotes stick to surfaces (or each other) to establish biofilms to allow for gene exchange, the cell should have pili, which are longer, more rigid, less numerous (than fimbriae) extensions on the outside of the cell that can be used to adhere to surfaces, move, and aid in gene transfer through conjugation to allow the cell to move in response to magnetic fields, it would need to have magnetosomes, which accumulate magnetic iron into membranous inclusions

Assume you want to design a prokaryotic cell that can survive in extremely cold environments, forms sticky biofilms on surfaces, can resist drying, is able to carry out gene exchange, and is magnetotactic (moves in response to magnetic fields). What structures/features would you give the organism and why?

cell wall, gram negative bacteria have an outer membrane and thin peptidoglycan layer, gram positive lack outer membranes and have a thick peptidoglycan layer

Differences in what structure determine the gram status?

prokaryotic ribosomes have a lower overall mass and diameter than eukaryotic ribosomes (antibiotics often target these structural differences), prokaryotes have a lesser sedimentation rate as well

How are prokaryotic and eukaryotic ribosomes different?

(1) while both bacteria and archaea are prokaryotic, they are different (2) prokaryotes are all unicellular and lack membrane bound organelles (3) prokaryotes have unique size, shape, and arrangements

Prokaryotic Cell Basics

provide structure and shape to a cell, protect cell from hypotonic environments

What are the functions of the cell wall?

incredibly resistant, not metabolically active, dormant, persist for long periods of time

What are the primary characteristics of endospore formation?

gram negative and gram positive

What are the two basic types of bacterial cell walls?

cytoplasm, ribosomes, genetic material

What are three intracellular structures that exist within prokaryotes?

gram negative, because it has no cell wall and therefore no peptidoglycan layer so it will not be able to retain the purple (positive) color

What gram property would mycoplasma be and why?

a cell without a cell wall would experience a membrane that would shrink in on itself (crenation), but a cell with a cell wall would experience plasmolysis as the cytoplasm volume decreases and the plasma membrane shrinks away from the cell wall

What happens to a cell with a cell wall in a hypertonic solution compared to a cell without a cell wall in a hypertonic solution?

complex polysaccharides that are unique to prokaryotes, chains are attached to other chains by cross links of four amino acids (tetrapeptides)

What is peptidoglycan made of?

peptidoglycan

What is the core component of the cell wall?

the net movement of water from an area of low solute concentration to an area of higher solute concentration across a selectively permeable membrane, does not require energy to occur, cells experience osmotic stress when they are placed in environments where their water balance is disrupted

What is the definition of osmosis?

rod like extensions made of protein (many present), unique to prokaryotes, allow for attachment to other bacteria or to surfaces

What is the function of a fimbriae structure?

allow for motility, taxis (movement in response to a stimulus like light or chemicals)

What is the function of a flagellum structure?

provide protection from our defenses, allow for attachment to surfaces

What is the function of a glycocalyx (capsule) structure?

only one or few present, unique to prokaryotes, used specifically to transfer DNA from one bacterial cell to another, also allow for adherence to surfaces and in some cases movement

What is the function of a pilus structure?

survival, when conditions are unfavorable, a vegetative metabolically active cell develops and endospore, then the rest of the cell except for the endospore is shed away and the endospore remains metabolically inactive indefinitely until conditions are favorable, then it germinates and becomes a metabolically active vegetative cell again

What is the purpose of endospore formation?

thin peptidoglycan layer, plasma membrane, periplasmic space, outer membrane, LPS, porin

What structures exist within a gram negative cell?

thick peptidoglycan layer, plasma membrane, periplasmic space, teichoic acid

What structures exist within a gram positive cell?

Bacillus and Clostridium

What two gram positive genera are discussed as endospore formers?

prokaryotic DNA is organized into single circular chromosomes located in the nucleoid region of the cell, which has no boundaries and is not enclosed by a membrane

Where do you find prokaryotic genetic material?

acid fast staining technique detects a waxy lipid called mycolic acid in cell walls, just as it is hard for crystal violet to enter these cells, nutrients and gases also face challenges in entering acid-fast cells, as a result, acid-fast bacteria grow slowly, this stain is important for identifying causative agents of leprosy and tuberculosis

Why are mycobacterium and nocardia considered to be from an acid-fast genus?

the phospholipid bilayer is a selective barrier that separates the cells cytoplasm from the external environment, it is a bilayer so that the hydrophilic heads of the phospholipids can interact with the watery environment inside and outside the cell, the hydrophobic tails face inward to be sheltered from the water

Why do cell membranes exist as bilayers?

in a hypertonic environment there is more solute outside of the cell than inside which causes water to move from the inside of the cell to the outside environment until there is no difference in solute concentration on either side of the cell's membrane, in a hypotonic environment there is more solute inside the cell than outside which causes water to move from the outside of the cell to the inside environment for the same reason

Why does a cell lose water in a hypertonic environment and gain water in a hypotonic environment?

selective permeability allows gases, water, and other small noncharged substances to diffuse into and out of the cell without assistance, ions and larger polar substances require specific protein membrane transporters to enter or exit a cell

Why is it important that the cell membrane is selectively permeable?

it is a bacteria species that have a sterol enriched plasma membrane and no cell wall

Why is mycoplasma an exception to gram positive and gram negative?

it is not enclosed in a nuclear envelope

Why is the nucleoid region not a true nucleus?

the IV saline solution likely created a hypertonic external solution, for the red blood cells to have shrunk, the solute concentration outside of the RBC's plasma membrane must be higher than the solute concentration inside of the cell's plasma membrane (the solute concentration in the IV saline solution may have been higher than 0.9%)

You administered an IV saline solution to a patient but his symptoms are not improving. After looking at the red blood cells microscopically you notice that many have shrunk and look distorted. What is the explanation for this?