CH1-3 micro

Who mapped the 1854 Soho cholera deaths and what did he find?

Dr. John Snow mapped deaths household by household and found the Broad Street public water pump was the point source

What action halted the 1854 cholera epidemic?

Removing the Broad Street pump handle - done before germ theory was accepted

What pathogen causes cholera?

Vibrio cholerae - a Gram-negative comma-shaped rod with a single polar flagellum

How is cholera transmitted?

Fecal-oral route through contaminated water

What are the symptoms of cholera?

Sudden "rice water" watery diarrhea and vomiting with up to 1 liter of fluid lost per hour leading to dehydration and muscle cramps and hypovolemic shock

Is Vibrio cholerae invasive?

No - it is noninvasive and infects the mucous barrier of the small intestine

What does cholera toxin (CT) cause?

Electrolyte and water loss through secretory diarrhea

At what pH does Vibrio cholerae grow?

Alkaline conditions (pH 8 to 9.5)

Which O antigen serotypes cause cholera?

Only O1 and O139 (out of about 150 O antigen serotypes)

What is the El Tor biotype?

A cholera biotype that survives longer and is more infectious

What is the incubation period of cholera?

About 2 days

How is cholera treated?

Oral rehydration therapy (replace lost water and electrolytes) - antibiotics can speed recovery

What conditions let epidemic cholera spread?

Contaminated water with poor sanitation - especially where sewage treatment is absent or defective

Curviform bacteria

Curved Gram-negative rods that generally cause enteric (intestinal) diseases

Vibrio shape and habitat

Comma-shaped rods with a single polar flagellum found in saltwater

Campylobacter shape

Short spirals or curved rods with one flagellum

Helicobacter shape

Tight spirals with several polar flagella

What type of organism is Cyclospora cayetanensis?

A eukaryotic protozoan in phylum Apicomplexa and an obligate intracellular parasite

Other Apicomplexa examples

Malaria and babesiosis and toxoplasmosis and cryptosporidiosis

Disease caused by Cyclospora

Cyclosporiasis - relapsing watery gastroenteritis

2026 Cyclospora outbreak facts

18445 lab-confirmed US cases since May 1 2026 (vs 1180 from May to Aug 2025) - third largest foodborne outbreak in US history - likely culprit shredded lettuce

Cyclospora oocyst appearance

Spherical and 8-10 µm

Why are freshly shed Cyclospora oocysts not infectious?

They are unsporulated and need 1-2 weeks in the environment to sporulate

Does Cyclospora spread person to person?

No - it spreads by ingesting food or water contaminated with sporulated oocysts (fresh produce)

Cyclospora life cycle inside the host

Sporozoites invade the small intestine epithelium then multiply asexually then sexually forming oocysts that are released into the environment

How is Cyclospora diagnosed?

Modified acid-fast stain (pink/red) and UV autofluorescence (neon blue under 330-380 nm UV) and PCR

Cyclospora treatment

Trimethoprim-sulfamethoxazole (TMP-SMX) - a folate pathway inhibitor

Is Cyclospora killed by chlorine or iodine?

No - it is resistant to both - cooking food and boiling water work and washing helps but is not 100% effective

Why is Cyclospora hard to track?

Long incubation (weeks) and FoodNet monitoring ended after budget cuts (the CDC Cyclospora lab went from 11 people to 3)

Prokaryote

A microscopic unicellular organism that lacks a nucleus and membrane-bound organelles

Eukaryote

A cell with a nucleus and membrane-bound organelles - can be unicellular or multicellular

What are the two prokaryote domains?

Bacteria and Archaea

Archaea

Environmental extremophiles with novel biochemistry

Algae

Photosynthetic aquatic protists - studied in phycology

Protozoa

Single-celled protists that may be pathogenic - studied in protozoology

Fungi

Decomposers that can be single or multicellular - studied in mycology

Helminths

Worms with microscopic life stages that are diagnosed microscopically - studied in parasitology

Are arthropods microbes?

No - but they can cause or transmit disease

Virus

An acellular particle with a capsid and nucleic acid that grows only inside host cells (obligate intracellular) - studied in virology

What are smaller relatives of viruses?

Viroids and prions

Typical size of most bacteria

1 to 10 µm

How long have bacteria-like organisms existed?

About 3.5 billion years

Role of microbes in photosynthesis

Light-fueled conversion of carbon dioxide to organic material

Role of microbes in decomposition

Breakdown of dead matter and wastes into simple compounds

Biotechnology

Production of foods and drugs and vaccines using living organisms

Genetic engineering

Manipulating the genes of organisms to make new products

Bioremediation

Using living organisms to remedy an environmental problem

Parasite

An organism that lives on or in a host and damages it

Pathogen

A microbe that does harm

Infectious disease statistics from lecture

Nearly 2000 microbes cause disease with about 10 billion new infections and 12 million deaths per year worldwide

Spontaneous generation

The early belief that life could arise from nonliving or decomposing matter (such as flies from manure)

Who disproved spontaneous generation?

Louis Pasteur - supporting the Theory of Biogenesis

Biogenesis

Living things can only arise from other living things

Who was Antonie van Leeuwenhoek?

Dutch linen merchant (1632-1723) and first microbiologist - his single-lens microscope magnified up to 300X and he was first to observe living microbes

Order of the scientific method

Question then hypothesis then theory (after many repeats and extensive evidence) then law or principle (if extremely compelling)

What did Tyndall and Cohn show?

Some microbes have heat-resistant forms - Cohn identified them as bacterial endospores

What does sterility require?

Eliminating all life forms including endospores and viruses

Why are endospores important?

They are the most resistant cells on earth - surviving boiling and UV and drying and disinfectants and possibly millions of years

What did Oliver Wendell Holmes observe?

Mothers of home births had fewer infections than those who gave birth in hospitals

What did Ignaz Semmelweis find?

Infections correlated with physicians coming directly from the autopsy room to the maternity ward

What did Joseph Lister introduce?

Aseptic techniques - chemical disinfection of hands before surgery and heat for sterilization

Germ theory of disease

Many diseases are caused by microbes growing in the body and not by sins or bad character or poverty

Louis Pasteur's contributions

Showed microbes cause fermentation and spoilage and disproved spontaneous generation and developed pasteurization and demonstrated germ theory

Robert Koch's contributions

Established Koch's postulates and identified the causes of anthrax and TB and cholera and developed pure culture methods

Koch's postulate 1

The microorganism must be found in abundance in all organisms with the disease but not in healthy organisms

Koch's postulate 2

The microorganism must be isolated from a diseased organism and grown in pure culture

Koch's postulate 3

The cultured microorganism should cause disease when introduced into a healthy organism

Koch's postulate 4

The microorganism must be reisolated from the inoculated diseased host and identified as identical to the original agent

Taxonomy

Organizing and classifying and naming living things - formal system started by Carl von Linné

Three parts of taxonomy

Classification (orderly grouping) and nomenclature (naming) and identification (determining traits for placement)

Levels of classification in order

Domain then Kingdom then Phylum then Class then Order then Family then Genus then Species

Three domains of life

Archaea and Bacteria and Eukarya

Binomial nomenclature

Two-name system - Genus (capitalized) and species (lowercase) both italicized or underlined (Staphylococcus aureus)

Phylogeny

The natural relatedness between groups of organisms

Evolution (as described in lecture 1)

All new species originate from preexisting species - usually progressing toward greater complexity

Molecule

A chemical substance formed when two or more atoms combine

Compound

A molecule made of two or more different elements

Formula (mass) weight

The sum of the atomic masses of all atoms in a molecule

Chemical bond

Forms when atoms share or donate or accept electrons to form molecules and compounds

Three types of chemical bonds

Covalent and ionic and hydrogen

Covalent bond

Atoms share electrons

Nonpolar covalent bond

Electrons shared equally

Polar covalent bond

Electrons shared unequally (like water - oxygen slightly negative and hydrogens slightly positive)

Single vs double covalent bond example

H2 has a single bond and O2 has a double bond

Ionic bond

Atoms donate and accept electrons (example - Na+ and Cl-)

Hydrogen bond

A weak bond between hydrogen and other atoms

Solution

A mixture of one or more solutes dispersed in a dissolving solvent

Solute vs solvent

Solute is what dissolves (Na+ and Cl-) and solvent is the dissolving medium (H2O)

Hydrophilic

Dissolves in water

Hydrophobic

Repels water

Amphipathic

Has both hydrophilic and hydrophobic properties

What does water ionization release?

Hydrogen ions (H+) and hydroxyl ions (OH-)

pH

The negative logarithm of the H+ concentration - scale runs 0 to 14

pH below 7 / at 7 / above 7

Acidic / neutral / basic (alkaline)

Does more H+ mean higher or lower pH?

Lower pH (more acidic)

Organic chemicals

Compounds containing carbon bonded to hydrogens

Why is carbon so versatile?

It has 4 outer electrons so it forms single or double or triple covalent bonds and can make linear or branched or ringed molecules

Functional groups

Accessory molecules that bind to organic compounds and give the whole molecule unique reactive properties

Hydroxyl group is found in

Alcohols and carbohydrates

Carboxyl group is found in

Fatty acids and proteins and organic acids