Exam 2 Bacteria & Archaea 9/28 Flashcards
Bacteria can take many different shapes
Spherical (s. coccus, pl. cocci)
Rod-shaped (s. bacillus, pl. bacilli)
Comma-shaped (s. vibrio, pl. vibrios)
Spiral (s. spirillum, pl. spirilla)
Pleiomorphic (varied shapes)
Vibiancy
Dormancy mechanism caused by stress, lowering metabolism to sleeping state
Bacteria can also assume multicellular organizations
Hyphae (branching filaments of cells)
Mycelia (tufts of hyphae)
Trichomes (smooth, unbranched chains of cells)
Size of bacteria can vary greatly
Usually smaller than eukaryal cells
SMALL eukaryal cells are usually >5 μm in diameter
The cytoplasm
Liquid/gel environment where all metabolic and functional activity occurs
The Nucleoid (nuclear region)
irregularly shaped region in bacteria and archaea
usually not membrane bound (few exceptions)
location of chromosome and associated proteins
supercoiling
nucleoid proteins (HU)
Plasmids
extrachromosomal DNA
exist and replicate independently of chromosome
episomes
contain few genes that are non-essential
May exist in many copies in cell
Inherited stably during cell division
Can be lost during cell division
Classification of plasmids based on mode of existence, spread, and function
Ribosomes
complex structures
entire ribosome
*bacterial and archaea ribosome = 70S
*eukaryotic (80S) S = Svedburg unit
^*(note: eukaryotic are slightly larger than bacterial and archaea ribosomes)
bacterial and archaeal ribosomal RNA
16S small subunit = 30S
23S and 5S in large subunit = 50S
archaea have additional 5.8S in large subunit (also seen in eukaryotic large subunit)
proteins vary
The cytoplasm
What else is in the cytoplasm of bacterial cells?
A stew of macromolecules
Inclusion bodies may also be present
Polyhydroxybutyrate granules
Sulfur globules
Gas vesicles
Carboxysomes
Magnetosomes
Inclusions
Common in all cells
granules of organic or inorganic material
some are enclosed by a single-layered membrane
storage of nutrients, metabolic end products, energy, building blocks
Magnetosomes
bacterial cytoskeleton
The cytoskeleton is a series of internal proteins
Keeping everything in the cell
Move things to the right locations in cells.
Some cytoskeleton proteins are involved in cell wall synthesis during cell division (FtsZ and MreB).
Other cytoskeletal proteins are involved in moving internal items (e.g., plasmids, magnetosomes).
Bacterial Cell Envelope
Plasma membrane
Cell wall
Layers outside the cell wall
The plasma membrane
ALL cells have a plasma membrane (PM).
Interior/exterior
Usually composed of a phospholipid bilayer with embedded proteins
Plasma Membrane Functions
encompasses the cytoplasm
selectively permeable barrier
interacts with external environment
Bacterial Lipids
The PM may have sterol molecules called “hopanoids” in it to help with stability across temperature ranges
Membrane Proteins
peripheral
- loosely connected to membrane
- easily removed
- Make up 20 – 30% of membrane proteins
integral
- amphipathic
- Carbohydrates often attached
- carry out important functions
- Can move laterally in the membrane
- may exist as microdomains (patchwork)
Membrane Proteins Functions
ATP production/energy production
Transportation through the membrane
The plasma membrane: getting things in
O2 and CO2 - diffuse across readily
H2O – aquaporins
Osmosis is the flow of water across the PM toward the side with a higher solute concentration.
How do organisms take up nutrients?
Microbes can only take in dissolved particles across a selectively permeable membrane
Must be able to take up specific molecules
Must concentrate nutrients against a gradient
microorganisms have developed a number of different transport mechanisms to accomplish this
facilitated diffusion – all microorganisms
active transport – all microorganisms
group translocation – Bacteria and Archaea
endocytosis – Eukarya only
Passive Diffusion
molecules move from a region of higher concentration to one of lower concentration between the cell’s interior and the exterior
Not energy dependent
The rate of diffusion depends on the concentration gradient
H2O, O2, and CO2 often move across membranes this way
Facilitated Diffusion
similar to passive diffusion
movement of molecules is not energy dependent
direction of movement is from high concentration to low concentration
size of concentration gradient impacts rate of uptake
differs from passive diffusion
uses membrane bound specific carrier molecules
smaller concentration gradient is required for significant uptake of molecules
A concentration gradient spanning the membrane drives the movement of molecules
Is reversible depending on concentration of molecules
The gradient can be maintained by transforming the transported nutrient into another compound
effectively transports glycerol, sugars, and amino acids
more prominent in eukaryotic cells than in bacteria or archaea
No energy required
Not useful to bacteria and Archaea that live in environments with low concentrations of nutrients
rate of facilitated
diffusion
rate of facilitated
diffusion increases
more rapidly and
at a lower
concentration
diffusion rate
reaches a plateau
when carrier
becomes
saturated
Active Transport
energy-dependent process
move molecules against a gradient
concentrates molecules inside cell
involves specific carrier proteins (permeases)
Types of Active Transport
3 types: Primary, Secondary, Group Translocation
Primary Active Transporters (ABC Transporters) – use energy provided by ATP hydrolysis to move substances against a conc gradient
Secondary Active transporters (major facilitator superfamily MFS Transporters) – couple the potential energy of ion gradients to transport substances
ABC Transporters
primary active transporters use ATP
ATP-binding cassette transporters
observed in Bacteria, Archaea, and eukaryotes
Consist of :
2 hydrophobic membrane spanning transporter proteins
2 cytoplasmic associated ATP-binding domains
Considered to be uniport – transports one molecule at a time
ABC Transporter Function
Leads to ATP hydrolysis which provides energy for opening channel and movement of solute
Secondary Active Transport
major facilitator superfamily (MFS)
uses ion gradients to co-transport substances
symport - two substances both move in the same direction
transport of lactose using lactose permease in E. coli transports lactose and a proton simultaneously into the cell
antiport - two substances move in opposite directions
transport of sugars and amino acids in E. coli while pumping sodium out
