Bacterial Genetics, Metabolism, and Structure

Flashcards on Bacterial Genetics, Metabolism, and Structure.

Genetics

Molecular structures and processes for heredity and variation.

Three major aspects in bacterial genetics

Structure and organization of genetic material, replication and expression of genetic information and mechanisms for genetic alteration and exchange among organisms.

Nucleic Acids

Carry genetic info

DNA

Deoxyribonucleic acid

RNA

Ribonucleic acid

DNA

Deoxyribose sugars and four bases adenine and guanine (purines) thymine and cytosine (pyrimidines)

RNA

Ribose sugars and four bases uracil (U) replaces thymine (T)

mRNA

protein sequence

tRNA

transfers amino acids

rRNA

ribosomes

ncRNA

gene expression

Nucleotides

sugar + phosphate + base

ATP

adenosine triphosphate

GTP

guanine triphosphate

CTP

cytosine triphosphate

Base Sequence

The order of the bases are along a DNA or a RNA strand and provides the information that codes for proteins synthesized by the cells (genetic code)

Antiparallel

5′ phosphate of one strand opposed to the 3′ terminal of the other strand

Complementary Base Pairing

A - T (U) and G - C

Gene

A DNA sequence that encodes for a specific product (proteins or RNA)

Organism’s genome

Is made up of all genes, includes the chromosomes and the mobilome (extrachromosomal mobile genetic elements)

Bacteria

Chromosome is not located within membrane-bound organelle, Chromosome is double-stranded, circular and supercoiled and must unwind to express genes

Fungi and parasites

Chromosomes located within a nuclear membrane and Chromosomes are linear

Viruses

DNA (or RNA) is contained within the protein coat and may be double or single stranded

Plasmids

Are double-stranded “miniature” chromosomes, made up of several genes that mediate replication and transfer or encode for products with a special function (e.g., resistance), Not vital to survival; may be lost during replication and May have multiple per cell and can become incorporated into chromosome

Transposons

Pieces of DNA that move between plasmids and chromosome, Not separate entities and do not replicate independently and May be simple transposons (insertion sequences) or composite transposons (surrounded by insertion sequences)

Replication

Chromosomal DNA are relaxed, Strands of DNA are separated, New strands are synthesized on the replication forks, DNA polymerase adds nucleotides, Replication is terminated when the two forks meet (one parent, one daughter) and Cellular components split

Transcription

DNA base sequence is converted into RNA

Operon

RNA polymerase adds nucleotides and gene group controlled by one promoter

Translation

mRNA is translated into specific amino acid sequences, protein structure and function

transfer RNA (tRNA)

binds to ribosomes and mRNA (codon) to deliver appropriate AA

Regulation

Controls the transfer of information

Transcriptional

Genes that encode anabolic enzymes are repressed in the presence of an end product and Genes that encode catabolic enzymes are induced when the substrate to be degraded is present

Translational

Enzyme production is controlled at the protein synthesis level

Posttranslational

Regulation of enzymes (proteins) that are already synthesized

Constitutive genes

Some genes essential and always “on”

Mutation

The alteration of the organism’s genotype and one base, one gene, multiple genes

Genetic Recombination

Segment of DNA from original bacteria enters a second cell where DNA is exchanged

Transformation

Free (naked) DNA fragments from dead cells recombine with the recipient’s DNA in competent cells

Transduction

DNA is integrated into the recipient’s DNA via a bacteriophage

Conjugation

DNA is transferred between two living cells

Bacterial Metabolism

All the cellular processes required for an organism’s survival and replication

Simple diffusion

Water, oxygen, carbon dioxide

Active transport

Sugars, amino acids, inorganic ions with carrier molecules in membrane

Energy production

Adenosine triphosphate (ATP) generation

Biosynthesis

Uses precursor products from fueling processes to produce a variety of building blocks such as AA, fatty acids, sugars and nucleotides

Polymerization and Assembly

Anabolic reactions polymerize building blocks into macromolecules like lipids, lipopolysaccharides, proteins and nucleic acids

Eukaryotic

Fungi and parasites which are single or multicellular

Prokaryotic

Bacteria which are single celled and do not contain organelles

Prokaryotic

Cell wall with peptidoglycan, mycolic Acid and No cell wall

Bacterial Morphologic Characteristics

Range in size from 0.25 to 1 μm in width and 1 to 3 μm in length and Gram stain differentiates the bacterial cell wall – Gram-positive (purple color) and Gram-negative (pink color)

Cell Envelope

Outer membrane (gram-negative only) with lipopolysaccharide (LPS), Cell wall (peptidoglycan; murein layer) Gram-positive—Contains a thick layer of peptidoglycan, Gram-negative—Contains thin layer of peptidoglycan and Acid fast—Contains waxy substances (e.g., mycolic acids)

Periplasm or periplasmic space (gram-negative only)

Between cell membrane and cell wall. Contains gel-like substances that capture nutrients and Contained enzymes

Cell membrane (Cytoplasmic membrane)

Deepest layer of the cell envelope. Contains proteins and enzymes that are vital to cellular metabolism and Serves as osmotic barrier

Capsule

Consist of a high-molecular-weight polysaccharide

Fimbriae

Serve as adhesins for attachment

Pili

May serve as an adhesin or for the passage of DNA

Flagella

Are primarily for motility

Cell Interior

Structures and substances bound internally

Cytosol

where all functions occur

Polysome

mRNA complexed with ribosomes

Inclusions

storage reserve granules

Plasmids

other genetic elements

Endospores

structural changes→ dormancy for survival under stress conditions

Base Sequence

The sequence of nucleotide bases (adenine, guanine, cytosine, and thymine in DNA or uracil in RNA) along a DNA or RNA strand. This sequence contains the genetic code, dictating the order of amino acids in proteins synthesized by the cells. The specific order determines the protein's function. Codons, which are triplets of bases, each correspond to a specific amino acid or a stop signal during protein synthesis.