Chapter 22 Prokaryotes: Bacteria and Archaea

Flashcards covering the history of microbiology, prokaryotic diversity, cell structures, metabolic processes, genetics, human diseases, and beneficial roles of bacteria and archaea.

In 1546, which Italian physician suggested that disease was caused by unseen organisms?

Girolamo Fracastoro

Who was the first person to observe and accurately describe microbial life?

Antony van Leeuwenhoek

What are the four postulates proposed by Robert Koch to prove a causal relationship between a microorganism and an individual?

1. The microorganism must be present in every case and absent from healthy individuals. 2. The agent must be isolated and grown in pure culture. 3. The same disease must result when the culture infects a healthy host. 4. The same microorganism must be isolated again from the diseased host.

What percentage of prokaryotes are estimated to be unknown and undescribed?

$90$ to $99\%$

What are the two domains that prokaryotes fall into?

Bacteria (Eubacteria) and Archaea

How old are the fossilized stromatolites found in Glacier National Park, Montana?

Nearly $1.5\,billion$ years old

What specific organism type is responsible for the green color in the hot springs of Yellowstone National Park?

Cyanobacteria

In which stage of biofilm development do hairlike appendages called pili permanently anchor bacteria to a surface?

Stage 2 (Irreversible attachment)

What is the typical diameter of most prokaryotes compared to eukaryotes?

Generally much smaller, with most being less than $1\,mm$ in diameter

Where is the single, circular, double-stranded DNA chromosome found in a prokaryotic cell?

The nucleoid region

How do prokaryotes primarily divide and exchange genetic material?

They divide by binary fission and exchange material through horizontal gene transfer (not sexual reproduction).

What are the three basic categories of bacterial shapes?

(a) Cocci (spherical), (b) Bacilli (rod-shaped), and (c) Spirilli (spiral-shaped)

What fundamental chemical difference exists between the plasma membranes of Bacteria and Archaea?

Bacterial lipids use ester bonds and are unbranched; Archaean membranes use ether linkages on a glycerol skeleton and may have branched hydrocarbons or tetraether polymers.

Which molecule is present in the cell walls of Bacteria but absent in Archaea?

Peptidoglycan

Which phylum of bacteria includes organisms like E. coli, Salmonella, and Yersinia pestis?

Proteobacteria (specifically Gamma Proteobacteria)

What is the difference between Gram-positive and Gram-negative bacteria regarding their cell wall structure and staining?

Gram-positive bacteria have a thick peptidoglycan wall and stain purple; Gram-negative bacteria have a thin layer of peptidoglycan and stain pink (retaining the counterstain).

What is the function of the S-layer in some bacteria and Archaea?

A rigid paracrystalline layer outside the cell wall often involved in adhesion.

How is a photoheterotroph defined in terms of carbon and energy acquisition?

Uses light as an energy source but obtains organic carbon made by other organisms.

What are the three types of horizontal gene transfer in prokaryotes?

1. Conjugation (cell-to-cell contact via pilus), 2. Transduction (mediated by bacteriophages), 3. Transformation (DNA uptake from the environment).

What is the role of the F plasmid in E. coli conjugation?

It serves as the fertility factor; $F^+$ cells contain the plasmid and produce a pilus to transfer the plasmid to $F^-$ cells.

What are auxotrophs?

Nutritional mutants that are studied using replica plating.

Which bacterium is the causative agent of Tuberculosis (TB)?

Mycobacterium tuberculosis

What is the primary cause of most peptic ulcers, and how is it treated?

Helicobacter pylori; treated with antibiotics.

Which Gram-negative spirochete bacterium causes Lyme disease?

Genus Borrelia

What specific toxin is produced by the E. coli O104:H4 strain that can lead to kidney failure?

Shiga toxin

Which nitrogen-fixing bacteria are found in aquatic environments and which are found in soil?

Anabaena (aquatic) and Rhizobium (soil)

What is the difference between mutualism, commensalism, and parasitism in symbiosis?

Mutualism: both benefit; Commensalism: one benefits and the other is unaffected; Parasitism: one benefits and the other is harmed.

What is bioremediation, and what is an example of its use mentioned in the notes?

The use of organisms to remove pollutants from water, air, and soil; used to clean up the Exxon Valdez oil spill.