Microbiology Chapter 4

Basic shapes of bacteria

1. Coccus 2. Bacillus 3. Spiral

Distinguishing characteristics of prokaryotes

1. DNA isn't enclosed w/in membrane-singular circularly arranged chromosome 2. DNA not associated w/histones 3. Lack membrane enclosed organelles 4. Cell walls almost always contain complex polysaccharide peptidoglycan 5. Divide by binary fission

Parts of a flagellum

1. Filament 2. Flagellin 3. Hook 4. Basal body

Two types of hairlike appendages in gram negative bacteria

1. Fimbriae 2. Pilli

Structure of plasma membrane

1. Lipid bilayer with hydrophilic polar head and nonpolar hydrophobic tails 2. Have protein molecules like peripheral proteins, integral proteins, and transmembrane proteins

More shapes

1. Stella-Star shaped 2. Haloarcula- rectangular flat cells (halophilic archaea) 3. Triangular cells

Two types of motility of pilli

1. Twitching motility 2. Gliding motility

Distinguishing characteristics of eukaryotes

1.DNA found in nucleus which is separated from cytoplasm by nuclear membrane and DNA is found in multiple chromosomes 2.DNA is consistently associated w/chromosomal proteins called histones 3. Have a # of membrane enclosed organelles 4. Cell walls are chemically simple 5. Cell division using mitosis-chromosomes replicate and an identical set is distributed into each of two nuclei. Guided by mitotic spindle

Extracellular polymeric substance (EPS)

A glycocalyx that helps cells in a biofilm attach to their target environment and to each other

Plasma (cytoplasmic) membrane

Aka inner membrane, is a thin structure lying inside the cell wall and enclosing the cytoplasm of the cell, consists primarily of phospholipids in prokaryotes

Motility

Altered by the basal body of flagella, bacteria cells can alter the speed and direction of rotation of flagella and thus are capable of various patterns, the ability of an organism to move by itself

Core polysaccharide

Attached to lipid A and contains unusual sugars, provides stability

Types of prokaryotes

Bacteria and archaea

Monomorphic

Bacteria maintain a single shape mostly, but environmental conditions can alter the shape

Atrichous

Bacteria that lack flagella

Peptidoglycan

Bacterial cell wall is composed of a macromolecular network of this, which is present alone or in combo w/ other substances. Composed of repeating disaccharide attached by polypeptides to form a lattice that surrounds entire cell. Disaccharide portion made of monosaccharides N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)

Integral proteins

Can be removed from membrane only after disrupting lipid bilayer and most penetrate membrane completely

Pleomorphic

Can have many shapes, not just one

Fimbriae

Can occur at poles of bacterial cell or can be distributed over entire surface of cell, have tendency to adhere to each other and to surfaces. Help form biofilms and help bacteria adhere to epithelial surfaces In body

Functions of glycocalyx

Can protect pathogenic bacteria from phagocytosis by cells of host, important component of biofilms, and can protect a cell against dehydration and viscosity may inhibit movement of nutrients out of the cell

Protoplast

Cellular contents that remain surrounded by the plasma membrane may remain intact if lysis doesn't occur, this is the wall-less cell and is typically spherical and still capable of carrying on metabolism

Repellant

Chemical signal is negative, and the frequency of tumbles increases as bacteria move away from stimulus

Chemotaxis

Chemical stimuli of bacteria

What happens when fimbriae are absent

Colonization can't happen and no disease ensues

Outer membrane of gram negative cell

Consists of lipopolysaccharides, lipoproteins, and phospholipids. Provides barrier to certain antibiotics

Vibrios

Curved rods

Application of alcohol

Dehydrates peptidoglycan of gram + cells to make it more impermeable to the crystal violet iodine but on gram - cells it dissolves outer membrane and leaves small holes in thin peptidoglycan layer thru which crystal violet diffuse

Penicillin

Destroys bacteria by interfering with formation of peptide cross-bridges of peptidoglycan thus preventing formation of functional cell wall

Lysis

Destruction caused by rupture of plasma membrane and loss of cytoplasm

Streptococci

Divide and remain attached in chain like patterns

Sarcinae

Divide in 3 planes and remain attached in cube like groups of eight

Staphylococci

Divide in multiple planes and form grape like clusters or broad sheets

Tetrads

Divide in two planes and remain in groups of four

Gram negative cell walls

Don't contain teichoic acids, consist of one or very few layers of peptidoglycan and an outer membrane. Peptidoglycan bonded to lipoproteins in outer membrane and is in periplasm

Axial filaments (endoflagella)

Especially found in spirochetes, these are bundles of fibrils that arise at the ends of the cell beneath an outer sheath and spiral around the cell

O polysaccharide

Extends outward from core polysaccharide and is composed of sugar molecules. Functions as an antigen and is useful for distinguishing species of gram negative bacteria

Amphitrichous

Flagella at both poles of the cell

Polar

Flagella that are at one or both poles or ends of the cell

Peritrichous

Flagella that are distributed over the entire cell

Monotrichous

Flagella that are polar and are a single flagellum at one pole

H antigen

Flagellar protein that is useful for distinguishing among serovars

Bacteria shape size

From 0.2 to 2.0 nanometers in diameter and 2-8 nanometers in length

Periplasm

Gel like fluid between the outer membrane and the plasma membrane, has a high concentration of degradation enzymes and transport proteins.

Flagellin

Globular protein of flagella that is arranged in several chains that intertwine and form a helix around a hollow core

Possible structures external to the prokaryotic cell wall

Glycocalyx, flagella, axial filaments, fimbriae, sand pili

Safranin

Gram negative bacteria are colorless after alcohol wash so this turns cell pink or red

Spirochetes

Helical and flexible, move by means of axial filaments which resemble flagella but are contained within a flexible external sheath

Spirilla

Helical shape like a corkscrew and fairly rigid bodies

Attractant

If a stimulus has a chemotactic signal that is positive

Capsule

If glycocalyx is organized and firmly attached to the cell wall. Presence of this can be determined by negative staining

Slime layer

If glycocalyx is unorganized and only loosely attached to the cell wall

Teichoic acids

In cell walls of gram positive bacteria, consist primarily of an alcohol and phosphate. Two types are lipoteichoic acid and wall teichoic acids. Regulates movement of cations and polysaccharides provide antigenic variation

Hook of flagella

In flagella attached to Flagellin and is slightly wider and contains a different protein

Mycolic acid

In mycobacterium and nocardia is a hydrophobic waxy lipid in their cell wall that prevents uptake of dyes including those used in the gram stain. Forms a layer outside thin layer of peptidoglycan

Diplobacilli

In pairs after division, always divide across short axis so fewer groupings then cocci

Transmembrane proteins

Integral proteins that penetrate the membrane completely

Archaea cell walls

Lack cell walls or have unusual walls composed of polysaccharides and proteins but not peptidoglycan and contain substance similar to peptidoglycan called pseudomurein which contains N-acetylalosaminuronic acid instead of NAM and lacks D-amino acids found in bacterial cell walls. Cannot be gram stained but appear gram - bc don't have peptidoglycan

Phototaxis

Light stimulus of bacteria

Wall teichoic acid

Links to peptidoglycan

Lipoteichoic acid

Links to plasma membrane

Lipid A

Lipid portion of LPS and is embedded in the top layer of the outer membrane. When gram - bacteria die they release lipid A which functions as an endotoxin. Also responsible for symptoms associated with infections by gram - bacteria (fever, dilation of blood vessels, shock, and blood clotting)

Glycolipids

Lipids attached to carbohydrates, help protect and lubricate cell and involved in cell to cell interactions

Flagella filament

Long outermost region of flagella, constant in diameter and contains the globular protein Flagellin

Selective permeability

Main function of plasma membrane is to serve as a selective barrier through which materials enter and exit the cell

Hairlike appendages of gram negative bacteria

Many gram negative bacteria contain hairlike appendages that are shorter, straighter, and thinner then flagella and are used for attachment and transfer of DNA rather than motility. Consist of a protein called pillin arranged helically around central core

Streptobacilli

Occur in chains

Cell wall

Of bacterial cell, a complex semirigid structure responsible for the shape of the cell, surrounds underlying fragile plasma membrane. Prevents bacterial cells from rupturing when the water pressure inside the cell is greater than that outside the cell, helps maintain shape, and point of anchorage for flagella.

Lipopolysaccharides (LPS)

Of outer membrane, large complex molecule that contains lipids and carbohydrates and consists of three components 1) lipid A 2) core polysaccharide 3) an O polysaccharide

Spiral bacteria

One or more twists

Coccobacilli

Oval and look a lot like cocci

Basal body

Part of flagella, anchors flagellum to cell wall and plasma membrane

Fluid mosaic model

Phospholipids and protein molecules in membranes aren't static but move freely within membrane surface

Chromatophores (thylakoids)

Pigments and enzymes involved in photosynthesis are found in infoldings of plasma membrane that extend into cytoplasm

Twitching motility

Pilli extends by addition of subunits of pilin, makes contact with a surface or another cell, and then reacts (power stroke) as pillin subunits are disassembled (grappling hook model)

Lophotrichous

Polar flagella that are a tuft of flagella coming from one pole

Mycoplasma

Prokaryote that have no cell walls or very little wall material, these are the smallest known bacteria that can grow and reproduce outside living host cells. First mistaken for viruses bc of size and lack of cell walls. Have sterols in plasma membrane that protect from lysis

Glycocalyx

Prokaryotes secrete this on the surface of the cell, means sugar coat, general term for substances that surround the cell -viscous gelatinous polymer that is external to the cell wall and composed of polysaccharide or polypeptide

Glycoproteins

Proteins attached to carbohydrates, help protect and lubricate cell and involved in cell to cell interactions

Porins

Proteins in outer membrane that form channels and permit the passage of molecules like nucleotides, disaccharides, peptides, amino acids, vitamin B12 and iron

Bacillus

Rod shaped, "Little staffs"

Movement of bacteria

Run in a continuous direction and tumble to change direction

L forms

Some members of the genus Proteus as well as other genera can lose their cell walls and swell into these irregularly shaped cells. May form spontaneously or in response to penicillin or lysozyme and can live and divide repeatedly or return to walled state

Flagella

Some prokaryotic cells have this, long filamentous appendages that Propel bacteria

Lysozyme

Specifically targets cell wall of prokaryote and damages it

Coccus

Spherical, "berries" can be oval, round, elongated, or flattened on one side

Spiral

Spiral shaped

Crystal violet stain

Stains both gram positive and gram negative cells purple because the due enters cytoplasm of both cell types

Structure of polypeptide

Tetrapeptide side chains-4 amino acids attached to NAMs in the backbone, occur in alternating pattern of D and L forms. Parallel Tetrapeptide side chains bonded by peptide cross-bridge

Single bacilli

The majority, single rods

Taxis

The movement of a bacterium toward or away from a particular stimulus

Polypeptides

The peptide portion of peptidoglycan

Gliding motility

Type of motility associated with pilli, the smooth gliding movement of myxobacteria.

Conjugation (sex) pilli

Type of pilli that are used to bring bacteria together allowing transfer of DNA from one cell to another. This pilus called an F+ cell connects to receptors on the surface of another bacterium of its own species or a different species

Pilli

Usually longer then fimbriae and number only one or two per cell. Involved in motility and DNA transfer.

Iodine

When applied it forms large crystals with dye that are too large to escape thru the cell wall

Spheroplast

When lysozyme is applied to gram - cells the wall isn't destroyed to same extent as gram + cells and some of outer membrane remains and cellular contents, plasma membrane, and remaining outer wall layer are called this which is also a spherical structure

Osmotic lysis

When protoplasts and spheroplasts burst in pure water or very dilute salt or sugar solutions bc water molecules from surrounding fluid rapidly move into and enlarge the cell which has a much lower internal concentration of water

Diplococci

When they divide to reproduce they remain attached to each other, these are pairs

Peripheral proteins

are easily removed from membrane by mild treatments and lie at inner and outer surface of membrane

Serovars

variations within a species of gram negative bacteria