Chapter 4: Survey of Prokaryotic Cells

What are characteristics of the cells of living things?

• Basic shape- spherical, cubical, cylindrical

• Internal content- cytoplasm, surrounded by a membrane

• DNA chromosome(s), ribosomes, metabolic capabilities

What are the two basic cell types?

eukaryotic and prokaryotic

What does eukaryotic mean?

true nucleus

What does prokaryotic mean?

before nucleus

What are the characteristics of Life?

• Reproduction and heredity- genome composed of DNA packed in chromosomes; produce offspring asexually/sexually

• Growth and development

• Metabolism- chemical and physical life processes

• Movement and/or irritability- respond to stimuli- self propulsion of many organisms, homestasis

• Cell support, protection, and storage mechanisms like cells walls, vacuoles, granules, and inclusions

• transport of nutrients and waste

• The ability to grow

Nucleoid

found in prokaryotes like bacteria and archea

What is the plasma membrane made by?

phospholipid bilayer

What are the 2 major groups of appendages?

• Motility- flagella and axial filaments

• Attachment or channels- fimbriae and pili

Glycocalyx

surface coating

What are the flagellar arrangements?

Monotrichous, Lophotrichous, Amphitrichous, Peritrichous

Monotrichous

single flagellum at one end

Lophotrichous

small bunches emerging from the same site

Amphitrichous

flagella at both ends of cell

Peritrichous

flagella dispersed over surface of cell

Fimbriae

fine, proteinaceous, hairlike bristles emerging from the cell surface

What is the function of fimbriae?

adhesion to other cells and surfaces

Pili

rigid tubular structure made of pilin protein that is found only in gram negative cells

What is the function of pili?

join bacterial cells for partial DNA transfer called conjugation

What is biofilm?

community of microorganisms attached to a surface

cells stick together

What is the cell envelope?

external covering outside the cytoplasm that is composed of the cell wall and cell membrane that maintains cell intergrity

What are the 2 different groups of bacteria demonstrated by Gram stain?

Gram-positive and Gram negative bacteria

Gram Positive bacteria

thick cell wall composed primarily of peptidoglycan and cell membrane

Gram-Negative bacteria

outer cell membrane, thin peptidoglycan layer, and cell membrane

What does the cell wall determine?

determines cell shape to prevent lysis due to changing osmotic pressure

What is the primary component of cells walls?

peptidoglycan

Peptidoglycan

unique macromolecule composed of a repeating framework of long glycan chains cross linked by short peptide fragments

What are the names of the alternating glycans in peptidoglycan?

• NAG- N-acetyl glucosamine

• NAM- N-acetyl muramic acid

Characteristics of Gram Positive Cell Wall

• 20-80 nm thick peptidoglycan

• Includes: teichoic acid and lipoteichoic acid

• Some cells have a periplasmic space, between cell membrane and cell wall where bacteria fold proteins

What does teichoic acid and lipoteichoic acid in Gram Positive Cell do?

• function in cell wall maintenance and enlargement during cell division

• move cations across cell envelope

• stimulate a specific immune response

Characteristics of Gram Negative Cell Wall

• Inner and outer membranes and periplasmic space between them contains a thin peptidoglycan layer

• Outer membrane contains lipopolysaccharides (LPS)

• 8-11 nm

What are lipopolysaccharides (LPS) in Gram Negative Cells?

• Lipid portion (endotoxin) may become toxic when released during infections and cause sepsis

• May function as receptors and blocking immune response

• contain porin proteins in upper layer- regulate molecules enetering and leaving cell

Number of layers in gram positive

One

Number of major layers in gram negative

Two

Chemical composition of gram positive

Peptidoglycan

Teichoic acid

Lipoteichoic acid

Mycolic acids and polysaccharides

Chemical composition of gram negative

Lipopolysaccharide (LPS)

Lipoprotein

Peptidoglycan

Porin proteins

Overall thickness of gram positive

Thicker (20-80 nm)

Overall thickness of gram negative

Thinner (8-11 nm)

Does gram positive have an outer membrane?

No

Does gram negative have an outer membrane?

Yes

Periplasmic space in gram positive

Narrow

Periplasmic space in gram negative

Extensive

Permeability to molecules in gram positive

More penetrable

Permeability to molecules in gram negative

Less penetrable

Can some bacterial groups lack a typical cell wall structure?

Yes, some examples include mycobacterium and Nocardia

Gram-positive cell wall structure w/lipid mycolic acid (cord factor)

Pathogenicity and high degree of resistance to certain chemicals and dyes

Basis for acid-fast stain used for diagnosis of infections caused by these microorganisms

Characteristics of some prokaryotes that have no cell wall like Mycoplasma

cell wall is stabilized by sterols

Pleomorphic- can take on many different shapes

Fluid Mosaic Model

phospholipid bilayer with embedded proteins

polar lipid molecules have polar head(hydrophilic) and non-polar tails(hydrophobic)

Phospholipid bilayer functions

Providing site for energy reactions, nutrient processing, and synthesis

Passage of nutrients into the cell and discharge of wastes

Cell membrane is selectively permeable

Cell Cytoplasm

dense gelatinous solution of sugars, amino acids, and salts

is 70-80% water which serves as solvent for materials used in all cell function

What are the components of a nucleoid?

Chromosome and plasmids

Chromosome

single, circular, double stranded DNA molecule that contains all the genetic information required by a cell (housekeeping genes)

Plasmids

free small circular, double stranded DNA

Not essential to bacterial growth and metabolism

used in genetic engineering- readily manipulated and transferred from cell to cell

Ribosomes

made of 60% ribosomal RNA and 40% and is the site of protein synthesis that consists of 2 subunits

Translates RNA —> protein

What are the 2 subunits?

Large and small

What is the Svedburg unit of ribosomes in prokaryotic cells?

Large- 50S

Small- 30S

Ribosome(total)- 70S

Inclusions and granules (internal structure)

intracellular storage bodies

vary in size, number, and content

bacterial cell can use them when environmental sources get depleted

can be made by proteins, carbs, lipids, etc

Cytoskleton

internal network of protein polymers that is closely associated with the cell wall

gives the cell its shape

What are endospores?

inert, resting, cells produced by some G+ genera like Clostridium, Bacillus, and Sporosarcina

What are the 2-phase life cycle of endospores?

Vegetative cell and endospore

Vegetative cell

metabolically active and growing

Endospore

when exposed to adverse environmental conditions; capable of high resistance and very long term survival

Sporulation of endospore

formation of endospores and is the hardiest of all life forms

withstands extremes in heat, drying, freezing, radiation, and chemicals

not a means of reproduction

Germination of endospores

return to vegetative growth

Characteristics of endospores

dehydrated, metabolically inactive w/thick coat

Longevity verges on immortality, 250 million years

resistant to ordinary cleaning methods and boiling; only way to destroy is to pressurize them at 120oC for 20-30 mins

What are the 3 basic shapes?

Coccus, bacillus, spirillum

Coccus

spherical shape

Bacillus

rod shaped

Coccobacillus

very short and plump that looks like a football

vibrio

gently curved rod

Spirillum

helical, comma, twisted rod, corkscrew shaped

Spirochete

spring like shape

Pleomorphism

variation in cell shape and size within a single species and some species are noted for their pleomorphism

Cocci bacterial arrangement

singles

Diplococci- in pairs

Tetrads- groups of fours

Irregular clusters

chains

Cubical packets (sarcina)

Bacilli bacterial arrangement

Diplobacilli

Chains

Palisades

What measurment is bacteria measured in?

micrometers

Photosynthetic bacteria

use photosynthesis, can synthesize required nutrients from inorganic compounds

What are examples of photosynthetic bacteria?

cyanobacteria(blue-green algae), green and purple sulfur bacteria, and gliding, fruiting bacteria

Cyanobacteria (Blue-Green algae)

gram negative cell walls

extensive thylakoids(where they do photosynthesis) with photosynthetic chlorophyll pigments and gas inclusions

produces ½ of the O₂ that we breath

Green and Purple Sulfur Bacteria

photosynthetic

contain photosynthetic pigment bacteriochlorophyll

Do not give off oxygen as a product of photosynthesis

Bacteriochlorophyll

used in an-oxygenic photosynthesis and produces sulfur compounds instead

obligate intracellular parasites

grow and reproduce inside a cells of a host

What are examples of obligate intracellular parasites?

Rickettsias and Chlamydias

Rickettsias

Very tiny, gram-negative bacteria

most are pathogens

cannot survive or multiply outside of a host cell

Rickettsia rickettisii- Rocky mountain spotted fever

Chlamydias

tiny and not transmitted by arthropods (ticks, fleas)

Chlamydia trachomatis

severe eye infection and one of the most common sexually transmitted diseases

Chlamydia pneumoniae

lung infections

Is archaea related more to Eukarya or Bacteria?

more closely related to Eukarya

Archaea

contain unique genetic sequences in their rRNA and have unique membrane lipids and cells walls

only organism with ether bonds

most are ancient and unchanged

Type of ribosomes in archaea

70S but structure is similar to 80S

Cell membrane lipids in bacteria

Fatty acids with ester linkages

Cell membrane lipids in archaea

Long-chain, branched hydrocarbons with ether linkages

Habitats of archaea

live in the most extreme habitats in nature, extremophiles

What are archaea adapted to?

heat, salt, acidic pH, pressure, and atmosphere

What is included in archaea?

methane producers, hyperthermophiles (hot loving), extreme halophiles (salt loving), and sulfur reducers