Microbial Growth and Endospores

• Vegetative cells begin endospore formation by forming a septum, which separates one copy of the chromosome.
• A forespore and mother cell form.
• The forespore is engulfed by the mother cell.
• Endospore layers develop around the engulfed forespore chromosomes, and the mother cell starts to degenerate.
• The mother cell lyses.
• The endospore fully forms.

Microbial Division

• Binary fission is the process by which a microbe divides.
• Time is the duration it takes for one cell to double.
• Exponential growth occurs when something increases over time, relevant in the context of viral infections, biofilm formation, and antibiotic resistance.
• Sustaining exponential growth requires nutrients, space, and a favorable environment.
• Microbial growth is measured by growing bacteria in liquid culture.
• Microbes avoid death by becoming dormant, like endospores, hunkering down to wait for better conditions.

Quorum Sensing

• Quorum sensing involves bacteria assessing the surrounding microbe population, which can alter behavior through gene expression.
• High-density triggers motility, prompting movement to infect tissue, impacting bacteria.
• Slow-growing bacteria can also cause disease, tuberculosis has a doubling time of 25 to 30 hours.

Bacterial Growth Phases

• Lag phase: pathogens adapt.
• Log phase: cells replicate.
• Stationary phase: growth plateaus.
• Death or decline phase: pathogen numbers decrease.
• Microbial growth rate is affected by food access, environmental conditions, temperature, space, pH, and pressure.
• Growth optimum refers to when a bacterium is isolated in pure culture with neutral pH.
• Ecological niche defines where organisms exist within the environment and how they adapt.
• Microbial growth is influenced by pH, lactic acid, CO2 production, and O2 changes.
• Adding salt changes solidity and forces chemicals out of the pathogens' way.
• Temperature is a factor, and different groups have different temperature optimums; heat can kill, cold prevents division or reproduction.
• Tissues lose access to blood and become anoxic.
• Obligate aerobes depend on aerobic respiration.
• Facultative anaerobes show more growth than O2 but can go without.
• Microaerophiles need oxygen.
• Pathogens or microbes that thrive in specified chemical makeups of the body and can only grow under narrow modifying temperature and pH are key ways to prevent passing growth and food.
• Biosafety levels range from 1 (harmless if consumed) to 4 (most dangerous).
• A fomite is an inanimate object, transmitting disease.

Antimicrobial Treatments

• Disinfection.
• Sanitation.
• Sterilization (boiling, bleach, radiation, microwaves).
• Antiseptics are determining.
• Sterilization compounds do not remove endotoxins or prions.
• The death curve illustrates the relationship between disinfectant exposure time and microbial cell destruction.
• Diffusion determines how good the disinfectant is, where it cannot grow again.
• Antimicrobials are all agents relating to micro groups.
• Antibiotics target bacteria specifically.
• Eukaryotic antimicrobials target non-bacterial microbes.
• Anti-protozoan target non-fungal eukaryotic microbes.
• Antivirals target viruses.
• Antihelminthics are for parasitic worms.
• Antiseptics affect living tissue but do not cause harm.
• Penicillin's target, peptidoglycan, makes it unique because it does not affect human cells, which lack it.
• Broad-spectrum antibiotics may cause unintended harm, like post-surgery complications, by killing everything.
• Narrow-spectrum antibiotics are prescribed when the exact target is known.
• Main challenge in drug development is that some drug targets are very close to us so it is hard to find a specific cell to target.
• Antifungal mechanisms do not harm human cells because they have cholesterol, not ergosterol.
• Antiprotist treatments on spore structures are a good target because cells are similar.
• Parasitic worms: Drugs with selective toxicity are developed to target parasitic worms, which is hard to achieve.
• Treating replication makes a virus tough to deal with.
• HIV drugs increase inhibitors and reverse transcriptase inhibitors.
• Antifungal medications target ergosterol or its biosynthesis and fungal cell walls.
• Anti-prozone MEDS treat targets that are shared with a cell which can lead to greater side-effects.

Definitions

• Genes determine characteristics like hair color, eye color, and disease risk.
• Griffith Experiment: Heat killed smooth virulent bacteria mixed with rough non-virulent bacteria converts the rough strain to virulence.
• A virulence factor helps a microbe cause disease, capsules encoded by a set of genes.
• Vertical gene transfer occurs from parent to offspring.
• Horizontal gene transfer occurs between non-parent organisms.
• Transformation is direct uptake of DNA from the environment that uses special enzymes.
• Conjugation is exchange of genes through physical contact.
• Transduction is virus-dependent when transferring microbial genes, microbes, then gain new genes fast.
• Bacteria are numerous and divide quickly, which speeds up evolution.
• PAN provides access to a huge library from all organisms.

Selection types

• Artificial selection is found in natural populations and the traits can arise due to mutations and sex.
• Gene transfer introduces new functional genes acting on raw material; Variation sees some die with reproduction reliant on antibiotic resistance.
• Horizontal gene transfer introduces AMR genes that transform a bacterium's ability to resist stresses then the antibiotics kill most of the non-resistant cells living in rich population of antibiotic resistant cells lastly these traits can be transferred again to other bacteria.
• Superbugs: Multi-drug resistant bacteria are untreatable, even with last-resort antibiotics; resistance comes from antimicrobial compounds or synthetic resistant genes in the wild.

Mechanisms of Pathogenicity

• Disease is a damaged condition that is a mutation or genetic
• A sign is measurable whereas a symptom is how one feels.
• Not all diseases are caused by pathogens.
• Sickle cells block blood vessels and nutrients for the body.
• When infecting tissue, use building blocks to reproduce without expending energy.
• The apical complex enables pathogens to attach to and invade host cells.
• Good bacteria digest food, while bad bacteria produce toxins.
• An infection is the replication of wrong microbes causing harm.
• Meningitis is a dangerous infection affecting the nervous system and lungs.
• Infections acquired at the hospital are nosocomial, while healthcare transmitted infections are iatrogenic.
• Pathogenesis: exposure, adherence, invasion, colonization, toxicity, and damage.
• As the spectrum of virulence (ID50) increases, the disease becomes worse.
• Primary pathogens always cause disease.
• Opportunistic pathogens have the potential to cause disease.
• Secondary infections break down past any barriers.
• Bacteria needs the immune system to be avoided.
• Streptococcus is dangerous because it enters deep tissue, infects, and enters the bloodstream, stopping immune system response.

Mechanisms of Virulence

• Motility.
• Adhesion (e.g., Velcro-like).
• Enzymes.
• Glycocalyx.
• Avoiding the immune system.
• Outer structure for attachment.
• Lacking outer structure allows changes in cells when lacking a cell wall.
• Endotoxin is the outer membrane of Gram-negative bacteria.
• Exotoxin is actively produced, exploring to sell and have more specific targets more toxic.
• LD50 is a dose that will kill 50% of subjects.
• Neurotoxins cause muscle spasms strong enough to break bones.
• Botox paralyzes muscles, stopping neurotransmitter production and wrinkles.
• Super antigens clamp two cells together, so the alert never stops, creating two viruses.

Public Health and Epidemiology

• Cholera is caused by the vibrio cholerae and is dehydration due to diarrhea.
• Etiology is study of the causes of a disease.
• Morbidity is a state of being diseased.
• Prevalence is active cases.
• Incidence is new case numbers.
• Sporadic is random and rarely.
• Endemic goes above threshold.
• An influenza segmented genome allows for antigenic drift which can then attack a single cell in shifting form that the immune system will not recognize.

Types of Studies

• Observational: watching in your community
• Experimental: looking at the disease like vaccines
• modes of disease transmission

Reservoirs

• Passive carriers: touch a surface, then touch a patient.
• Active carriers: like salmonella.
• Direct contact: like kissing a baby.
• Indirect contact: a doorknob.
• Vehicle transmission: unsafe disposal of sewage.
• Vector transmission: a fly transmits it but doesn't cause it.
• Ways to prevent the spread are quarantining.
• Emerging diseases are equally and re-emerging diseases and are due to microbial evolution such as antibiotic resistance and horizontal gene transfer.