aWzsdxjkl Flashcards
Rod Shape bacteria (E. coli) length
1-1.5 micrometers wide
2-6 micrometers long
Streptococcus (Round) length
0.8-1 micrometer in diameter
Divide in only one division plane, and they remain attached to one another after division
Staphylococcus (Round) length
they stay attached together during cell division but they divide in random division planes.
Bacterial cell envelope
The substance outside of the cell wall that contains the cell
Perieable barrier
lets some things in and out, but not others
Bacterial plasma membrane
Inner most layer in the cytoplasm
Required for all living cells if broken the cell dies
Anchor point
certain receptors for detecting and responding to chemicals in the surrounding environment, for transport systems
The plasma membrane is__
asymmetric and made of two major components: lipids that make up the amphipathic bilayer
membrane proteins
Membrane proteins
either peripheral (loosely connected to membrane and easily removed), or integral proteins (which pass through the membrane and are amphipathic, like the lipids- where hydrophobic regions anchored in the core of the hydrophilic core of the lipid bilayer)
Integral proteins
carry out some of the most important functions in the membrane; many of them are transport proteins used to move materials in and out of the cell, while others are involved in energy conserving processes
The integral proteins with regions exposed to the outside of the cell, allow for interaction of the cell with the outside environment
Microbes
need a source of energy to thrive and survive: high energy ATP molecule is the energy currency
Facilitated diffusion:
substances move across the plasma membrane through transport proteins that are carriers or channels
Active transport:
transport of solutes to higher concentrations (against a gradient).
Primary Active transport
use energy provided by ATP hydrolysis to move substances against concentration gradient without modifying them
uniporters: move a single molecule across membrane
Secondary Active transport
potential energy of ion gradients to transport substances against concentration gradient without modifying them
They are all cotransporters (they move two substances simultaneously; there is antiporter and symporter)
Bacterial cell wall
essential for almost all bacteria since it helps maintain shape and protect the cell from osmotic lysis
(like a balloon popping)
Gram positive vs Gram Negative
(remember that Gram positive bacteria stains purple, Gram negative bacteria stains red or pink)
Gram negative bacteria are more diverse and more common than gram positive bacteria
This differential staining is actually due to the fundamental differences in the structure and arrangement of the cell walls
Cell walls of typical Gram positive bacteria consist of
a single 20-80 nanometer thick layer of peptidoglycan outside the plasma membrane
Gram negative bacteria have two distinct layers, a____
2-7 nm thick layer covered by a 12-14 nm thick outer membrane
Capsules
well organized and not easily washed off
Mostly made of polysaccharides, and other materials
They can be seen by negative staining using a light microscope
Slime layer
Helps to attach to the surface, including host tissues
Made of polysaccharides normally, but not easily observed under a light microscope
S-layers
protects the cell against pH and ion changes, osmotic stress, predatory bacteria and enzymes. It also maintains the cell shape and rigidity, protecting against host defenses for some pathogens.
Only in some bacteria
Made of protein
In gram negative bacteria, the S layer adheres non-covalently to the outer membrane
In gram positive bacteria, the S layer is associated with the surface of peptidoglycan
Bacterial cytoskeleton
Made of protein filaments that are similar to actin and tubulin in eukaryotes
Crowded space, the liquid component is the cytosol
Viscosity is ten times greater than water due to macromolecular crowding, affecting physical and chemical processes
Inclusions
Common in all cells
Bacterial Cytoskeleton Components
Inclusions
Bacterial ribosomes
Nucleoids
Plasmids
how bacterial chemotaxis works
Bacteria do not move around aimlessly, but rather they use motility to move away from harmful substances. The movement in response to chemical gradients is known as chemotaxis
move in response to non chemical cues like temperature
light
oxygen
osmotic pressure
Bacterial Attachment and Movement
Bacterial pili and fimbriae
Flagella
properties of bacterial endospores
Endospores– dormant cells that are formed within a mother cell.
They are only produced by certain species of bacteria:
rods; Bacillus and Clostridium genera
cocci; Sporosarcina
process of sporulation
Plants and fungi produce a large amount of spores for reproduction whereas bacterial spores are formed individually that are later germinated into a single cell.
Bacterial spore formation is not a reproductive strategy (unlike in plants and fungi), but rather it is a survival strategy during adverse conditions.
Sporulation cycle
Starts when growth slows down due to nutrient limitations. It is a survival mechanism that allows the bacteria to produce a dormant cell until nutrients become available again.
two stages: vegetative growth and survival as an endospore. Vegetative growth is the normal continuous cell growth cycle and division.
Sporulation cycle
- Chromosomal replication
- Asymmetric cell division– a septum forms off-center, creating two unequal cells
- Engulfment – mother cell engulfs the smaller cell, resulting in sm cell having two membranes
- Cortex formation– between the two membranes, a thick peptidoglycan layer (cortex) forms
- Coat formation– protective coat made of 80 different proteins
- Maturation
- Release– the mother cell/ sporangium lyses (breaks down), releasing the mature endospore into the environment
