botany

Prokaryotes

The smallest, simplest, and most abundant organisms on Earth.

Oldest Organisms

Prokaryotes are considered the oldest organisms in evolutionary terms.

Living Environments

Prokaryotes can live in extreme environments like ice, dark depths, boiling waters, and oxygen-free zones.

Viral Genome

Viruses consist of a genome that replicates itself within a living host cell.

Nucleoid

In prokaryotic cells, DNA is localized in a region called the nucleoid.

Plasmids

Small circular DNA that replicates independently of the chromosome in prokaryotes.

Chromosomes in Prokaryotes

Prokaryotic chromosomes are very long and may contain distinct granules known as inclusions.

Thylakoids

Membrane systems found in cyanobacteria and prochlorophytes that bear chlorophyll.

Plasma Membrane in Prokaryotes

Formed from a lipid bilayer, similar to eukaryotes.

Peptidoglycans

Polymers found in bacteria that give strength to cell walls.

Gram Positive

Bacteria whose cells retain dye and appear pink.

Gram Negative

Bacteria whose cells cannot retain dye and appear purple.

Glycocalyx

Layer around prokaryotes known as a capsule, important for infection and protection.

Flagella

Long, slender appendages that prokaryotes use for movement.

Fimbriae

Filamentous structures in prokaryotes that help in adhesion.

Pili

Longer than fimbriae, these structures help in conjunction.

Nanotubes

Tubules composed of cell wall material, plasma membrane, and cytoplasm.

Bacillus

A rod-shaped prokaryote.

Cocci

Spherical-shaped prokaryote.

Spirilla

Curved or spiral-shaped prokaryote.

Biofilms

Assemblages of prokaryotic cells attached to surfaces and enclosed in a matrix.

Binary Fission

The method by which prokaryotic cells reproduce, meaning 'dividing in two'.

Horizontal Gene Transfer

Mechanisms of genetic exchange in prokaryotes including conjugation, transformation, and transduction.

Conjugation

Prokaryotic version of sexual reproduction where genetic material is transferred between bacteria.

Transformation

Process where a prokaryote uptakes free DNA from the environment.

Transduction

DNA transfer method via viruses attacking bacteria.

Endospores

Dormant resting cells that increase survival capacity of bacteria.

Bacillus and Clostridium

Genera known for forming endospores.

Methanogens

Prokaryotes that produce methane gas and are strictly anaerobic.

Thermophiles

Archaea with membranes and enzymes stable at high temperatures.

Halophiles

Archaea that thrive in high salt concentrations.

Virion

The entire infectious virus particle consisting of the genome and coat.

Viral Symptoms in Plants

Degrees of dwarfing, stunting, mosaics, and ring spots are typical symptoms.

Insect Vectors

Common transmission agents of viruses in plants include aphids, leafhoppers, and whiteflies.

Hypersensitive Response (HR)

A mechanism for resistance activation dependent on pathogen recognition.

Systemic Acquired Resistance (SAR)

Mechanism induced by localized pathogen attacks requiring necrotic lesions.

Posttranscriptional Gene Silencing (PTGS)

A mechanism viruses induce upon infection that lowers mRNA levels.

Viroids

The smallest known agents of infectious disease, made of small, circular RNA.

Replication of Viroids

Occurs in the nucleus of host cells, mimicking DNA.

Aerobic Prokaryotes

Prokaryotes that require oxygen for respiration.

Anaerobic Prokaryotes

Prokaryotes that do not require oxygen and may even be killed by it.

Viruses and Host Cells

Viruses rely on host cells' machinery to replicate.

Bacteriophages

Viruses that specifically infect bacteria.

Photosynthetic Bacteria

Include cyanobacteria, purple bacteria, and green bacteria.

Cyanobacteria Oxygen Production

Responsible for a significant portion of Earth's oxygen production.

Ecological Role of Bacteria

Responsible for nitrogen fixation and recycling organic material.

Saprotrophs

Bacteria that recycle organic materials in the soil.

Human Disease Bacteria

Include pathogens like tuberculosis, cholera, and anthrax.

Commercial Uses of Bacteria

Used for producing drugs, vinegar, amino acids, and enzymes.

E. coli in Biofuels

Reengineered for producing biofuels similar to fossil fuels.

Prochlorophyte Characteristics

Photosynthetic bacteria containing chlorophylls a and b, but no phycobilins.

Prochlorococcus

The smallest known photosynthetic organism and a major component of phytoplankton.

Cyanobacteria Characteristics

May form filaments and grow in large masses.

Heterocysts

Specialized cells in filamentous cyanobacteria for nitrogen fixation.

Stromatolites

Layered chalk deposits produced by cyanobacteria.

Cyanobacteria in Acidic Waters

Cyanobacteria are typically absent in acidic waters.

Endospore Resistance

Endospores are resistant to heat, radiation, and chemicals.

Metabolic Diversity

Prokaryotes show vast metabolic diversity, including heterotrophy.

Antibiotic Resistance

A major concern due to the adaptive capabilities of bacteria.

Pathogen Transmission Mechanisms

Include insect vectors and mechanical wounds.

Cyanobacteria Dominance

The most significant photosynthetic bacteria, outcompeting other groups in various conditions.

Bacilli Formation

Bacilli usually separate after cell division.

Prokaryotic Biofilm Formation

Prokaryotes growing on surfaces tend to form biofilms.

Roles of Thermophiles

Archaea that stabilize enzymes and membranes at extreme temperatures.

Plant Viruses Movement

Divided into cell-to-cell movement and long-distance phloem movement.

Diversity of Prokaryotes

Includes various shapes such as rods, spheres, and spirals.

Common Features of Prokaryotes

Lack a nucleus and membrane-bound organelles.

Molecular Mechanisms in Pathogen Resistance

Include HR, SAR, and PTGS.

Mycoplasmas Characteristics

Bacteria without cell walls that can take on various shapes.

phytoplasma

no cell wall, very small, generally confined to conducting elements of the phloem known as sieve tubes

spiroplasmas

long spiral or corkscrew shaped cells very small, motile but lack flagella