9.Pili, Inclusions, Ribosomes and Genetic material Flashcards
What are fimbriae and pili
Proteic filaments protruding from the outer membrane of Gram - bacteria. Short, thin and slender and are present in more then one per cell
What’s the function of fimbriae and pili
Adhesion to other bacteria, other organisms or surfaces
Why is adhesion of fimbriae and pili molecule-specific
Because of specific adhesion proteins
What is the shape of fimbriae and what are they made of
They are short, slender tubes with helical shape
They are made of polymers of protein known as pilin
Where are adhesion proteins located in fimbriae
At the end for mediating cell adhesion
What are fimbriae used for
Forming multicellular structures like pellicle( on liquid) or biofilm(on solid)
What are pili similar to
To fimbria and are usually referred as ‘‘longer’’ filaments
What are pili and what are they made out of
Proteic filaments made of pilins
What functions can pili have
DIfferent pili can have different function in the cell(ex: adhesion to surfaces, cell aggregation, DNA transfer)
Are Archaeal pili similar to bacterial pili
Yes, but with differences in protein composition and some structural specificities
What’s twitching motility caused by?
type IV pili, elongating and retracting and therefore ‘dragging’ the cell
What are type IV pili made out of
Proteic units(pilins), polymerized at the base of the structure, in the plasma membrane
Are type IV pili both in Gram + and Gram- bacteria
Yes
What are specialized pili used for in Gram - bacteria
Specialized pili(sex pili) are used by Gram - bacteria for mating with other bacteria and transferring DNA
Where are sex pili created
In bacteria carrying conjugate plasmids(ex: F plasmid)
who can target specialized (sex) pili
Phages
What’s cytoplasm and what does it contain
Cytoplasm-part of the cell inside the plasm membrane. It consists of: cytosol, cytoskeleton, inclusion bodies, gas vesicles, nucleoid, plasmids, ribosomes
What’s cytoplasm made out of
Aqueous solution of several molecules and some organized structures. It’s extremely viscous
Is cytoplasm similar in both archaea and bacteria?
Yes
Are there cytoskeletal proteins in bacteria
Yes
What’s the function of cytoskeletal proteins in bacteria
-participate in cell division
- determine cell shape
-grant localization to proteins or other molecules
What’s exception to the rule that bacteria don’t have complexes with bi-layer membranes
Photosynthetic and nitrifying bacteria have groups of vesicles or tubular membranes in the cytoplasm, sometimes connected to the cell membrane
These vesicles contain large amount of proteins involved in energy production or conservation
Who has chlorosomes
Photosynthetic green bacteria
What do chlorosomes contain
Photosynthetic pigments, bacteriochlorophylls C,D,E
Where are chlorosomes located in the cell
They are closely associated with cytoplasmic membrane (inner face) by a basal plate and allow green bacteria to be distinguished from other photosynthetic bacteria
What are inclusion bodies
Inclusion bodies- aggregates of organic or inorganic substances in the cytoplasm
What kind of structure can inclusion bodies have
Crystal or amorphous
Where can inclusion bodies be located inside a cell
-floating free in the cytosol
-encapsulated in a proteic shell
-enclosed in a single-layer phospholipidic membrane
What functions can inclusion bodies have
Several, including nutrients storage and osmotic pressure control
What are examples of storage inclusions
-Glycogen granules(storage of glucose)
-Sulphur globules
-Poly-phosphate granules
-PHB granules
What are PHB granules
Poly- β-hydroxybutyrate, part of more general group of poly-hydroxyalkonate granules, storage of organic carbon. They have proteic single-layer shell
What are some other types of inclusion bodies
-Carboxaysomes- storage of CO2 and enzymes for sugar synthesis, allow CO2 fixation in cyanobacteria and other specialized bacteria
-Magnetosomes- aggregates of magnetite or greigite arranged in linear chain. They provide specialized bacteria(magnetotactic bacteria) orientation with Earth’s magnetic field. They can recognize north, south and down-direction, useful to determine depth of aquatic environment
What are gas vesicles used for
They appear in bacteria that live in liquid environment and that need floating capabilities
What are characteristics of gas vesicles
They are made of proteins only, have tubular shape and are permeable to gas only. They are usually arranged in groups, forming large structures of ‘Gas Vacuoles’
What is gas vesicles’ dimension and contribution to floating determined by
Extracellular pressure
What are ribosomes
Specialized sites for protein synthesis (translation)
Where can ribosomes be located inside the cell
In the cytoplasm or attached to plasma membrane (for synthesis of envelope associated proteins)
What are ribosomes made out of
Proteins and ribosomal(r)RNA
How many structural units does bacterial ribosome have and how can it be divided
70S
It has two subunits:
1. large 50S
2. small 30S
What do large and small subunits of bacterial ribosome contain
large-23S and 5S rRNA
small-16 S rRNA
Do bacterial subunits contain proteins
Yes, a lot (>50), many common to eukaryotes
How many structural units does archaeal ribosome have and how is it devided
70S
large 50S
small 30S
What to large and small subunit or archaeal ribosome contain
large: 23S and 5S rRNA; some Archaea have 5.8 S rRNA(like eukaryotes)
small: 16S rRNA
Do archaeal ribosomes have proteins that are common with bacteria only
no
What are 3 main groups that ribosomal proteins can be divided into?
- Universally conserved r-proteins that with the rRNA form common core;
2) Domain specific r-proteins (ex: bacteria-specific and eukaryote-specific; no archaea specific has been recognized)
3) R-proteins exclusively shared between archaea and eukaryotes ( also called archaea/ eukaryote-specific, A/E- specific)
Are r-proteins evenly distributed in the ribosome
No. Most of them are located on the solvent side of the subunits, leaving the subunit interface side to be dominated by rRNA
What function do r-proteins have
In ribosome biogenesis and ensuring optimal functioning of the ribosome. They have a role in stabilizing intrasubunit network, in forming the subunit contacts during protein synthesis and are docking sites for translation factors and other ribosome associated proteins during translation
What’s difference between prokaryotic mRNA and eukaryotic mRNA
Prokaryotic has several translation start sites while eukaryotic has single translation start site
What shape is chromosome in bacteria
It has 1-2 copies/cell, usually circular and rarely linear
It’s essential
Line up the 3 kingdoms from the largest to the smallest size of genome
Eukarya
Bacteria
Archaea
