Bacterial Cell Envelope and Plasma Membrane

The Cell Envelope

• The cell envelope comprises protective layers around a bacterial cell.
• It includes the plasma membrane and the cell wall.
• The structure depends on whether the bacteria is Gram-positive or Gram-negative.

The Plasma Membrane (Cell Membrane)

• Innermost layer of the cell envelope acts as a security gate controlling entry and exit.
• It's made of a phospholipid bilayer.
• Contains proteins both stuck and loosely attached.
• Some bacteria have hopanoids to stabilize the membrane, similar to cholesterol.
• Selective permeability regulates what enters and exits.
• Anchors cell structures like flagella.
• It's where ATP is produced via cellular respiration in bacteria and archaea.

The Bacterial Cell Wall

• A strong, flexible mesh outside the plasma membrane acts as a suit of armor.
• It prevents the cell from bursting in watery environments (osmotic lysis).
• It maintains cell shape, it helps with attachment like anchoring flagellum.
• Impacts bacteria interaction with antibiotics
• Composed of peptidoglycan

Peptidoglycan

• A unique structure found only in bacteria
• Made of NAM and NAG sugars linked in chains.
• Peptide cross-links hold the chains together.
• It functions like a chain-link fence with NAM and NAG as vertical wires and peptides as horizontal connectors.

Gram-Positive vs. Gram-Negative Bacteria

• There are two main types of bacterial cell walls differentiated by the Gram stain test
• Gram-positive bacteria have a thick peptidoglycan layer, no outer membrane, teichoic acids, a small periplasmic space, and are more sensitive to antibiotics & lysozyme.
• Gram-negative bacteria have a thin peptidoglycan layer, an outer membrane made of lipopolysaccharides (LPS), no teichoic acids, a large periplasmic space, and are less sensitive to antibiotics & lysozyme due to the outer membrane blocking access.

Importance of Gram Stain Differences

• Gram-positive bacteria like Staphylococcus and Streptococcus are easier to kill with peptidoglycan-targeting antibiotics like penicillin because their peptidoglycan layer is exposed.
• Gram-negative bacteria like E. coli and Salmonella are harder to kill because their outer membrane acts as a shield.
• Lysozyme breaks down peptidoglycan making Gram-positive bacteria more vulnerable.

Endotoxins

• Gram-negative bacteria have LPS in their outer membrane.
• Lipid A, a part of LPS, is a toxic molecule that can cause fever, inflammation, and septic shock when a bacteria dies.
• Antibiotics can worsen symptoms by releasing more endotoxins when killing Gram-negative bacteria.

S-layer

• A single layer of protein on some bacteria
• Typically produced in harsh conditions to protect the bacterial cell and help it attach to surfaces

Glycocalyx (Outer Coating of Bacteria)

• It is made of polysaccharides, sometimes with proteins
• Slime layer is loosely attached and more irregular
• Capsule is more structured and firmly attached

Capsule

• Almost always made of polysaccharides.
• Bacillus anthracis is an exception with its protein-based capsule.
• Vary in composition between bacterial species and even different strains
• Are visible under a light microscope
• Less porous and strongly attached to the cell wall
• Capsules help bacteria attach to surfaces and evade phagocytosis.
• Contribute to increased virulence, making bacteria more dangerous.
• Act as a means for bacteria to trick the immune system.
• Play a role in differentiating strains.
• Streptococcus pneumoniae has 90 different capsule types (serotypes),
• Used in vaccines like Prevnar 13, 20, and Pneumovax 23
• These vaccines train the immune system to recognize harmful bacteria

Cytoplasm

• Consists mostly of water (80%), along with proteins, carbohydrates, lipids, and ions.
• Nucleoid stores the main DNA.
• Plasmids store extra DNA with special traits.
• Ribosomes make proteins
• Inclusions store compartments

Nucleoid

• Bacteria have one or more circular, double-stranded DNA molecules.
• It stores essential genetic information.
• Lacks a nuclear membrane, unlike eukaryotic cells.

Plasmids

• Small and circular DNA molecules are separate from the chromosome.
• Transferrable between bacteria
• Carry nonessential genes that give useful traits, such as antibiotic resistance, toxin production, or special enzymes.
• Vertical gene transfer occurs from parent to offspring through cell division.
• Horizontal gene transfer happens between different bacteria, allowing the sharing of traits.

Ribosomes

• Their function is the creation of proteins
• Prokaryotic ribosomes (70S) are smaller than eukaryotic ribosomes (80S).
• Some drugs assist with bacterial infections by targeting bacterial ribosomes, without affecting human cells.

Inclusions

• Bacteria uses these the store nutrients inside the cytoplasm
• Sulfur granules store sulfur
• Phosphorus granules phosphorus
• Polyhydroxybutyrate (PHB) stores energy
• Magnetosomes help bacteria align with Earth’s magnetic field

Cytoskeleton

• Composed of protein filaments similar to actin in eukaryotic cells.
• Maintains cell shape.
• Help in cell division

Endospores

• Some Gram-positive bacteria form endospores to survive extreme conditions.
• Bacillus and Clostridium are examples of spore-forming genera
• Triggered by harsh conditions like starvation, heat, and UV radiation.
• Some endospores are from pathogens
• Clostridium botulinum leads to botulism
• Bacillus anthracis causes anthrax
• Food industry and the medical field are concerned with spores because they hard to kill (resistant to heat, chemicals, and radiation)
• Endospores are NOT for bacterial reproduction, they’re needed for bacterial survival when conditions become adverse

Sporulation and Endospore Formation

• Is considered bacterial "survival mode"
• The bacteria copies its DNA then divides unevenly, the smaller part that splits of is called the forespore
• The larger cell Engulps the forespore, wrapping it in an extra membrane
• This spore super tough, designed for harsh and adverse conditions

Clostridium Difficile (C. Diff) Facts

• Gram-positive cell wall type, stains purple under lab environments
• It holds a rod shaped cell morphology
• Lives in the large intestine and in soil
• 2-10% of healthy adults carry it without symptoms
• Pathogen: can cause pseudomembranous colitis—an infection of the colon.

C. Diff - Disease

• Most people stay asymptomatic as their gut biome keeps it under control
• Cause disease by releasing toxins
• These toxins attach to and get inside colon cells
• Cause apoptosis, breaking cell to cell connections, and causes inflammation
• All this presents as severe diarrhea, necrosis, and toxic megacolon

Symptoms

Facts about C. Diff in US

• 500,000 cases a year with 29,000 deaths
• Leading cause of health-care associated infectious diarrhea
• Greatest risk factors are being 65 years of age and recent antibiotic use
• Antibiotic use has also been seen to disrupt gut bacteria, causing intestinal dysbiosis

C.Diff Treatment

• Antibiotics will disrupt the bacteria, killing the C.Diff
• Infections often come back because dysbiosis remains
• An alternative treatment would be Fecal Microbial Transplantation (FMT), where a healthy donors feces is transplanted, resetting the dysbiosis

Eukaryotic cell motiliy

• Flagella is a whip used to help cells swim, human sperm use flagella to move
• There are a few flagella, but are long
• Cilia are short and are lots of tiny hairs
• Move in 2 patterns
• Power stroke: moves things
• Recovery stroke: Resets the position
• Cilia helps move dust and mucus out in the lungs

Flagella and Cilia structure

• Both have a special structure called a 9+2 microtubule arrangement
• 9 pairs of tubes in a circle, with 2 single ones in the middle
• The tubes are made of Tubulin
• These structures are 10x thicker than in bacteria
• They are covered in the cell membrane
• Help move the cell and things across the cell

Glycocalyx

• A Cells protective coating made of Polysaccharides
• Acts like a slimey shield
• Cell adhesion, protection, cellular comms

Cell Wall

• Fungi cells: Has chitin and glucans
• Plants & Algae cells: Made of cellulose
• Protozoans cells: Pellicle
• Animal cells: No cell wall

Plasma membrane

• Eukaryotic cells have sterols to prevent popping

Cytoplasm

• Cytosol: Liquid where everything floats
• Cytoskeleton: Gives structure, holds organelles, moves stuff around, helps change shape

Ribosomes

• NOT organelles: Do not have membranes, just the protein factories
• Made of rRNA and proteins
• Found floating or in the Rough ER
• Larger than bacterial Ribosomes
• Protein synthesis via mRNA instructions

Endoplasmic Reticulum (ER)

• Is THE cell factory, that makes fats and proteins and has 2 parts
• Smooth ER - Makes fats, oils, and steroids
• Rough ER - Makes ribosomes and proteins
• ER helps move materials in the cell

Golgi Complex

• Processes and packages proteins and fats from ER, and sends them off
• Creates Lysossomes

Types of vesicles

• Transport- Move stuff inside the cell
• Secretory - Take stuff outside the cell
• Lysosomes- Are garbage trucks
• Peroxisomes - Breakdown fats and chems
• They all fuse to drop off resources

Protein production

• Nucleus: Holds instructions for building proteins (DNA)
• Rough ER: Uses the instructions to build
• Golgi Complex: Sorts and packages the proteins
• Vesicles: Delivers the proteins -Secretion : (Exocytosis) - Some proteins leave the cell

Mitochondria

• Burns food for energy via ATP, holds own DNA

Chloroplasts

• Plants use light to make food via photosynthesis
• Both split via binary fission
• Early cells took in bacteria and slowly made them apart of the cell, the proof is they look like ancient bacteria, have circular DNA, have ribosomes, are susceptible to antibiotics, and divide

Eaukaryotic microbes

• can not see with naked eyes
• Fungi
• Break down living things --Single-celled --Multi celled
• Fungi are heterotrophic

Fungi

• Fungi cells also share similarities to human cells, making it difficult to target when curing infection
• Fleshy Fungi (Mushrooms, Toadstools, etc.)
• Molds grow in thread like strands from oxygen and break down living things
• Yeasts are tiny and round, with/without oxygen

Fungi reproduction types

• Budding: Where a new cell or "bud" appears or grows on the parent cell and pinches off
• Fragmentation: Where a mold breaks off and turns into an organism
• Binary fission: Where genetic material is duplicated and then divides into identical copies
• Yeasts have ability for asexual reproduction

Dimorphic Fungi

• Molds when cold, Yeasts when warm

Fungal Disease

• Slow to form and requires toxic treatments
• Skin, deeper tissue, surface diseases caused by contact exposure

Treatment

• Use creams for superficial and oral pills for systemic infections. Keep skin dry and from contaminated surfaces to prevent

Fungal review

• Human cells are harder to treat than bacteria
• Yeasts live in oxygen

Systemic Mycoses

• Dimorphic Fungi that grows and spores spreading throughout the body via mold and yeast exposure.

Protozoa facts

• Are infection causing and motile
• Eukaryootic, chemoheterotrophs, lack a cell wall
• Move via flagella, cilia, psuedopods; some are immobile

Protozoa types

• Trophozoite causes active infection
• Cyst is dormant

Flagellated protozoa

• Utilize little whip like flagellum or undulating membrane
• Invade: animal digestive, giardia, trichomanas

Protozoa Review

Giardia lamblia

• Are infection causing flagellated protozoa that infects via water sources.

Trichomonas vaginalis

• Anaerobic protozoa who causes STD characterized by vaginal discharge

Psuedopod protozoa

• move via "false feet" by moving its cytoplasm mass
• reproduce through fission and contain harmful parasites such as the Entamoeba histolytica

E Histolytica

• Parasite that causes amebiasis
• Can invade and damage hosts
• Spread as ingested cysts
• Damages intestines
• Causes bloody diahrea
• Can move to liver, lungs, brain
• Can be treated with metronidazole

Apicomplexa

• parasitic protozoa
• Non motile parasites
• invade host and reproduce
• include the parasite plasmodium

Facts about malaria

• Malaria is a disease caused by the protist plasmodium, which infects the liver and blood
• Transmitted to humans by mosquitos
• sporozoites infect the human blood
• sporozoites move to liver and divide into merozoites
• Red blood cells are infected and burst

parasitic worm facts

• Helminths are parasitic worms
• eat live insides
• multicellular and produce tiny eggs to spread
• Tapeworms: are long and steal nutrients using hooks
• trematodes: are flat and suck blood
• Nematodes: live in intestine, pinworm

worm facts

• Worms: can infest the anus, live eggs, and re-spawn in intestine

Atomic facts

• Atoms are an elements building blocks
• Protons: positive ions with mass
• Nuetrons: non charged ions with mass
• Electrons: Surround shell with negative charge: participate in bonding

Bonding facts

• Atoms bond to become more stable
• Bonding is determined by the # of protons
• Polar - unequal share of e-
• Non- polar- equal share of e-
• Ionic transfer e-
• Hydrogen weak holds h20

pH facts

• Measures solution
• More Hydrogen= acid
• 0-6= acid
• logarth scale
• bio
• Glucose fruc

Cell structure basics

• Glysotic - link sugars
• Proteins- enzyme, amino acids
• Lipids- membrane from triglycerides, fatty acids
• Nucleic: nucleotides, DNA/RNA sugar phosphate group

Protein facts

• Primary: sequence is maintained by bonds
• Seccond: spiral and folding shape
• Tertiary: 3D shape
• Quaternary: how sub units for protein function
• Hemoglobin

Dna 21 facts

• DA/TC/Gs paired with HT bond, phosphodiester bonds lock
• RNUA/UC and are not bonded