Chapter 1 - Humans and the Microbial World

Humans and the Microbial World

normal microbiota

enormous population of microorganisms in human body

how does the normal microbiota play an essential role in human health?

prevent disease (competes with disease-causing microbes), aid in digestion, promote development of immune system, influence metabolism

oil-eating microbes

naturally occurring in the ocean, feed on hydrocarbons in oil and break them down (combine with oxygen) to produce H2O and CO2

who are the founders/fathers of microbiology?

Leeuwenhoek and Hooke

Antony van Leeuwenhoek

made magnifying glass (microscope), studied lake water and observed animalcules

Robert Hooke

coined the term “cells,” discovered microbes, discovered microscopial mushroom (bread mold)

3 domains of living organisms (cellular)

bacteria, archaea, eukarya

non-living infectious agents (acellular)

viruses, viroids, prions

which cellular organisms make up prokaryotes?

bacteria and archaea

prokaryotic cells

do NOT have membrane-bound nucleus

eukaryotic cells

DO have membrane-bound nucleus and organelles

who proposed the 3 domains of life, including archaea (1977), and based on what?

Carl Woose, based on comparing DNA in 16S and 18S rRNA genes

spontaneous generation theory

life arises spontaneously from non-living things

francesco redi

demonstrated worms on rotting meat came from eggs of flies landing on meat; no eggs → no worms

john needham (1749)

demonstrated boiled broths still produced microorganisms

father spallanzi (1776)

contradicted Needham’s results; boiled broths longer and sealed flasks → broths remained sterile unless the necks cracked

controversy of spontaneous generation theory

some argued that heating the flask necks destroyed the “vital force” needed for spontaneous generation

Pasteur’s experiment (1860s)

ended arguments that unheated air or broths contained “vital force” necessary for spontaneous generation

biogenesis

production of living things from other living things

john tyndall

realized that broths made from hay contained heat-resistant microbes

Ferdinand Cohn (1876)

discovered endospores: heat-resistant form of bacteria

germ theory of disease

principle that microorganisms cause diseases

Robert Koch

identified specific causative agents of tuberculosis, suppuration, cholera, and anthrax

scientific naming

Genus (capitalized)

species name (not capitalized)

genus and species are italicized or underlined, genus may be abbreviated

examples of scientific naming

E. coli, E. coli, Escherichia coli, Escherichia coli

bacteria

single-celled prokaryotes, shaped cylindrical, spherical, or spiral

cell membrane and rigid cell wall (containing peptidoglycan), no membrane-bound organelles

have ribosomes and circular genome (located in nucleoid)

many move via flagella

reproduce via binary fission

archaea

single-celled prokaryotes, cell walls do NOT have peptidoglycan, rRNA different than bacteria and closer to humans

many are extremophiles

eukarya

single-celled or multicellular

fungi, algae, protozoa, helminths (worms)

which two eukarya make up protists?

algae and protozoa

fungi

use organic material for energy

size: range microscopic (yeasts) to macroscopic (molds and mushrooms)

algae

use sunlight for energy

size range microscopic (single-celled algae) to macroscopic (multicellular algae)

protozoa

use organic material for energy

single-celled microscopic organisms

helminths (worms)

use organic material for energy

size: adults typically macroscopic and often quite large, but eggs and larval forms are microscopic