Prokaryotes: Part 1

What are the two domains of prokaryotes?

Bacteria and Archaea

What percentage of bacteria are known and described?

Less than 1%

What is a characteristic of many Archaea?

Many Archaeans are extremophiles.

What is the size range of most prokaryotes?

Generally 1-2 µm in diameter.

How do prokaryotes reproduce?

Through binary fission.

What is the structure of prokaryotic DNA?

Single, circular, double-stranded DNA.

What is horizontal gene transfer (HGT)?

The exchange of genetic material between prokaryotes, not a form of reproduction.

What is the primary difference in cell walls between Bacteria and Archaea?

Bacteria have peptidoglycan, while Archaea lack peptidoglycan.

What type of ribosomes do prokaryotes have?

70S ribosomes.

What is the function of pili in bacteria?

Used in bacterial exchange of DNA.

What is the composition of the plasma membrane in Archaea?

Phospholipids made with ether linkages.

What is the role of FtsZ protein during binary fission?

Triggers the formation of a ring for cytoplasmic separation.

What is a glycocalyx?

A polypeptide or polysaccharide layer found in both Archaea and Bacteria.

What is the significance of the Tetraether polymer in Archaea?

Allows extremophiles to withstand high temperatures.

How do flagella differ between Archaea and Bacteria?

Archaeal flagella grow at the base and can rotate both ways, while bacterial flagella grow at the tip and rotate counterclockwise for movement.

What is the ecological role of prokaryotes?

They play diverse roles in ecosystems, including decomposition and nutrient cycling.

What is the primary method of genetic recombination in prokaryotes?

Horizontal gene transfer (HGT).

What are extremophiles?

Organisms that thrive in extreme environmental conditions.

What is the difference in gene expression between Archaea and Bacteria?

Archaeal transcription and translation are more similar to eukaryotes.

What is the primary means of cell division in prokaryotes?

Binary fission.

What is a key characteristic of prokaryotic cells compared to eukaryotic cells?

Prokaryotes lack membrane-bounded organelles.

What is the role of fimbriae in prokaryotes?

Used for attachment and formation of biofilms.

What is the evolutionary significance of Archaea?

An ancestor of modern Archaea is believed to have given rise to Eukarya.

What is the typical habitat of prokaryotes?

They can be found in diverse environments, including extreme habitats.

What is the main difference in cell size between prokaryotes and eukaryotes?

Prokaryotes are generally much smaller than eukaryotes.

What is the function of plasmids in prokaryotes?

Small extrachromosomal DNA molecules that can carry genes.

What is the significance of the circular DNA in prokaryotes?

It is a defining feature of prokaryotic cells, allowing for efficient replication.

What is the glycocalyx?

A gelatinous, sticky substance surrounding the outside of the bacterial cell, composed of polysaccharides, polypeptides, or both.

What are the two types of glycocalyces?

Capsule and slime layer.

Describe the capsule glycocalyx.

Composed of organized repeating units of organic chemicals, firmly attached to the cell surface, may prevent bacteria from being recognized by the host.

Describe the slime layer glycocalyx.

Loosely attached to the cell surface, water-soluble, and allows prokaryotes to attach to surfaces.

What is the S-layer in prokaryotes?

A rigid protein or glycoprotein layer found outside of peptidoglycan or outer membrane layers in some bacteria and Archaea.

What are flagella?

Slender, rigid, helical structures composed of the protein flagellin, involved in locomotion.

What is the function of pili?

Short, hairlike structures that aid in attachment and conjugation, and protect from the immune system.

What are the three basic shapes of prokaryotes?

Cocci (spherical), bacilli (rod-shaped), and spirilli (spiral-shaped).

What are endospores?

Structures that develop a thick wall around their genome and a small portion of cytoplasm when exposed to environmental stress, making them highly resistant.

What ecological relationships are described in prokaryotic symbiosis?

Mutualism (both benefit), commensalism (one benefits, the other unaffected), and parasitism (one benefits, the other harmed).

What is the role of bacterial cell walls?

Provide structure and shape, protect from osmotic forces, assist in attachment, and can be targeted by antibiotics.

What distinguishes Gram-positive bacteria?

They have a thick layer of peptidoglycan and stain purple in the Gram staining procedure.

What distinguishes Gram-negative bacteria?

They have a thin layer of peptidoglycan and a bilayer membrane containing lipopolysaccharides, staining pink in the Gram staining procedure.

What are teichoic acids?

Unique chemicals found in the cell walls of Gram-positive bacteria.

What is the lipid A portion of lipopolysaccharides?

It can cause fever, vasodilation, inflammation, shock, and blood clotting in Gram-negative bacteria.

Where can halobacteria thrive?

In hypersaline environments like the Dead Sea.

What is the significance of studying extremophiles?

It can lead to the discovery of new prokaryotic species with potential therapeutic and industrial applications.

What is the function of the bacterial capsule?

Aids in attachment and protects against the immune system.

How do endospores respond to environmental stress?

They develop a thick wall and can germinate when conditions improve.

What is the primary component of bacterial cell walls?

Peptidoglycan.

What happens to bacteria during Gram staining?

They are stained purple or pink based on the characteristics of their cell wall.

What is the ecological role of nitrogen-fixing bacteria?

They benefit plants by converting atmospheric nitrogen into a usable form.

What is the function of the slime layer in bacteria?

It allows prokaryotes to adhere to surfaces and provides protection.

What is the structure of Gram-negative bacterial cell walls?

They have a thin peptidoglycan layer and an outer membrane containing phospholipids, proteins, and lipopolysaccharides.

What is the role of the bacterial cell wall in resisting antimicrobial drugs?

It provides structural integrity and can be a target for antibiotic action.