AGRC1021 - Biological Concepts and Plant Science

Flashcards based on lecture notes about Bacteria and Archaea.

What are the key characteristics of prokaryotes?

Appeared 3.5 billion years ago, single-celled, lack internal membrane-bound organelles, small size (0.5 – 5.0 𝜇m), ability to rapidly adapt, and have cell walls.

What is Gram staining used for, and what information does it provide?

Gram staining differentiates bacteria based on cell wall structure. Gram-positive bacteria have thick walls that stain deeply, potentially indicating antibiotic susceptibility. Gram-negative bacteria have thinner walls and an outer membrane, which can impede drug entry.

What are capsules and slime layers, and what is their function in prokaryotes?

They are outer layers of polysaccharides or proteins on prokaryotes. Their function is to reduce dehydration and protect against the immune system of host organisms, for pathogenic species.

What is endospore formation and why is it important?

Endospore formation is a survival strategy used when resources are limited. The cell produces a copy of its DNA, forms a multilayered protective structure, removes moisture, and can survive in the soil for centuries.

What are fimbriae and what is their function?

Hairlike apendages that function to attach bacteria to surfaces, sometimes to other bacteria, or to host cells such as those of mucous membranes.

What is taxis and how do prokaryotes achieve motility?

Taxis is directed movement towards or away from stimuli. Flagella is the key mechanism for movement. Prokaryote flagella rotate using a complex protein motor embedded in the cell wall using a proton gradient as the power source.

How is the DNA organized in prokaryotes, and what are plasmids?

Prokaryotes have a single circular chromosome. DNA is not membrane bound and may also have smaller rings of DNA called plasmids, which carry a few genes.

How quickly do bacteria reproduce and evolve, and why is this significant?

Bacteria have reproductive cycles as short as 20 minutes, leading to high population sizes and rapid genetic mutations. This results in quick genetic diversity and rapid evolution, making bacteria highly adaptable.

Name three processes that allow prokaryotes to undergo genetic changes.

Transformation, Transduction and Conjugation.

How does transformation allow genetic recombination?

Foreign DNA uptake from the environment (absorbed and incorporated) to produce a new recombinant – often (but not always) from similar species

How does transduction allow genetic recombination?

Transfer from one prokaryote to another via a viral bacteriophage

How does conjugation allow genetic recombination?

Bacteria can temporarily join and one cell donates DNA to another through a hollow pilus.

What are some key differences between Bacteria and Archaea?

Archaea have some chemical and biochemical differences from Bacteria, and some live in extreme environments (Extremophiles).

Name three types of extremophiles.

extreme halophiles (high salt), extreme thermophiles (high heat), and anaerobes such as the methanogens (produce methane).

What is the significance of antibiotic resistance in bacteria?

The rapid rate of bacterial reproduction leads to antibiotic resistance. Broadscale use (and misuse) of antibiotics can hasten the process, and resistance genes can be transferred by horizontal gene transfer.

What are some positive uses of prokaryotes?

Prokaryotes can be used in food production (cheese, yogurt, beer, etc.), genetic research, production of vitamins/antibiotics/hormones, bioplastics/bioethanol production, and bioremediation of polluted ecosystems.