Bacterial Morphology, Structure of bacterial cells & bacterial spores

Viruses are prokaryotes or eukaryotes

Neither, they’re acellular

Commensalism

One organism benefits and the other one neither benefits nor is harmed

Mutualism

Both organisms benefits from the relationship

Parasitism

One organism (parasite) benefit while the host is harmed

Resident microbiota

Microbes that are alays present on or in the host

Transient microbiota

Microorganisms that can be present under certain conditions

Opportunist

Species of resident or transient microbiota that does not normaly cause disease but can under certains conditions

Shapes of bacterias

• Spherical: coccus

• Rod: bacillus

• Curved/spiral: spirillus

Pleomorphism

Ability of a bacteria to vary in forms under certains conditions

Cocci division

Can divide in one or more planes or randomly

Diplococci

Streptococci

Tetrads; division in 2 planes

Sarcinae; division in 3 planes

Staphylococci; grape like random division planes

Coccobacilli: short rod (intermediate btw cocci and bacilli)

Palisades bacilli

Diplobacili

Vibrio: comma sjaped

Spirillum: wavy shape

Spirochete: corkscrew

Bacteria cell structure

• Internal: cytoplasm (ribosomes, nucleoid, inclusions)

• Cell enveloppe (membrane usually surounded by a cell wall and also by a capsule or slime layer)

• External: Flagella, pili

No single bacteria posseses all of these structures at all times

Bacterial ribosomes

Called 70S ribosomes made of a 50S (large) and 30S (small) subunit

Mainly made of ribosomalRNA(rRNA)

Small subunit contains 16S rRNA and the large 23S and 5S

Inclusions are

Small body like granules or vacuoles

Cell wall

• Maintain cell shape

• Protect the interior of the cell from env changes

• Made of periplasmic space, peptidoglycan and outer membrane

Periplasmic space

Gap between cell membrane and cell wall (mostly in gram- smts in gram+)

Space occupied by periplasm

Digestive enzymes, transport proteins → destroy harmful substances and transport metabolites in cytoplasm

Peptidoglycan

• Responsible for cell wall rigidity

• Unique to bacteria

Outer membrane

• Mostly in gram-

• Bilayer membrane

• Made of lipopolysaccharide (O side chain/antigen and lipid A)

Lipid A is responsible for what

Toxic properties (endotoxin) - fever blood vessels dilatations

O antigen is responsible for what

Provoke immune response by infected host

Difference gram- & gram+

Gram-:

• Thinner cell wall

• Have outer membrane

• Thin layer of peptidoglycan

Gram+:

• Thicker layer of peptidoglycan

• Have teichoic acid (anchor wall to membrane)

• Outer membrane often absent

Glycocalyx

All substances containing polysacchardies external to cell wall, provide protection

Capsule

• Outside cell wall

• Help resisting phagocytosis

• Protect against desiccation

• Help cell to adhere surfaces

Slime layer

• Protect cell against drying

• Bind cells together

• Allow bacteria to adhere environment

Pili

Hair-like appendages, thinner and shorter than flagella

Pilli classification

Conjugation pili:

• Bigger than other pili

• Allow two cells to attach and conjugate

Attachment pili:

• Allow cell to attach to surface

Flagella

Motile organelle

Flagella part

• Filament

• Basal body (embededd in cell enveloppe)

• Hook (curved part link filament to basal body)

Does cocci have flagella

Rarely

When a bacteria has one flagella at one end, it’s called

Monotrichous

When a bacteria has two flagella at each end, it’s called

Amphitrichous

When a bacteria has two or more flagella at one or both end, it’s called

Lophotrichous

When a bacteria has flagella all over its surface, it’s called

Peritrichous

When a bacteria doesn’t have flagella , it’s called

Atrichous

Why spirochete coil like a corkscrew

Due to endoflagella (or axial filament)

Bacterial endospores

Resting stages produced by vegetatives cells of some bacteria

Very resistant

Can’t divide

Not metabolically active

Inside bacteria

Process that lead to endospore formation

Sporulation

What endospores will do

Develop in a new functional vegetative bacterial cell when condtions are optimal (germination)

List bacterial antigens (location, role)

Antigen A: Base of lipopolysaccharide layer of cell wall, endotoxin (fever, BV dilatation)

Antigen O: Side chain of LPS, provoke immune response

Antigen K: In capsule

Antigen F: In pili

Antigen H: in filament of flagella (flagellin)