MICRO - Introduction to Bacteriology

Eubacteria

Prokaryotes. Unicellular organisms. Have no true nucleus because they lack nuclear membrane. With peptidoglycan in cell wall. Lack membrane-bound organelles

Shape, Gram-stain, Oxygen Demand

Bacteria can be classified according to?

Bacteria

Usually fall within the ORANGE size range—along with red blood cells, some large viruses, and protists.

Cocci

May divide in one or multiple planes. When they reproduce and divide in one plane but remain attached, they produce cells in pairs.

Diplococci

Cocci in 1 plane arrangement

Tetrads

Cocci in 2 plans arrangement

Sarcinae

Cocci in 3 planes arrangement

Staphylococci

Cocci in multiple / random division / clusters arrangement

Streptococci

Cocci arranged in a linear fashion

Rod-Shaped

Bacili divide only across their short axis arrangement

Diplobacilli

Produced by a bacilli that can divide only in one plane

Streptobacilli

Can produce several cells connected to one another

Coccobacilli

Bacilli that are short and fat that kind of looks like a cocci and bacilli at the same time. Their shape is intermediate between a coccus and a bacillus

Spiral

Never straight. Have one or more twists. Have a variety of curved shapes

Vibrio

Curved or comma-shaped spiral bacterial arrangement

Spirillum

Rigid and wavy shape. Have a helical or corkscrew shape, but with rigid cell wall. Uses flagella for movement

Spirochetes

Corkscrew-shaped or helical and flexible. Use axial filaments for movement. Like flagella, but contained within a flexible external shape

Monomorphic

Maintain a single shape. Applicable to most bacteria

Pleomorphic

Shapes are determined by heredity. Assume different shapes

Glycocalyx

Outermost layer (followed by cell wall then cell membrane). Bacterial surface coating. General term used for substances that surrounds the cell. Secreted by prokaryotes on their surface. Composed of either polysaccharides, polypeptides, or both

Protection

Function of glycocalyx: since it is a bacterial surface coating, it is frequently exposed to harsh environment conditions

Antiphagocytic

Function of glycocalyx: Prevents the cell from being engulfed or phagocytosed by other cells. Minimizes the bacterium to be recognized as an antigen and be engulfed by phagocytic cells. Blocks the mechanism that phagocytes used to attach to and engulf the bacteria; thus, the encapsulated bacteria are more virulent than the uncapsulated ones

Slime Layer (Polypeptides)

Thinner glycocalyx. less organized. Loosely attached to the cell. Functions: Adhesion of the organism to surface host cell. Protects cell from dehydration and nutrient loss. Helps form BIOFILMS for organisms clinging together and form complex masses preventing from being dislodged from surfaces or membranes (e.g., gastrointestinal tract)

Capsule (Polysaccharides)

More organized glycocalyx. Firmly attached to the cell. Functions: Cell protection. Prevents bacteria from being phagocytised by other cells (antiphagocytic)

India ink method

Stains the background but not the cells

Anthony’s method

In this staining method, the cells appear purple surrounded by a pale blue halo

Crystal violet, Safranin, Methylene blue, Malachite green

What are the basic dyes (positive charge)?

India ink, Nigrosin, Eosin, Acid fuschin

What are the acidic dyes (negative charge)?

Flagella

Long filamentous appendages composed of the protein Flagellin. Attaches to the cell membrane and cell wall. Found in: all spirillas, half of the bacterias, and a few cocci.

Motility (Propellers)

Function of flagella: Flagellum allows bacteria to swim freely through an aqueous habitat

Highly Antigenic

Function of flagella: Flagellum bears the H antigen, an immunogenic identifying marker used to distinguish between variations among species

Filament, Hook

Part of flagellum: Can rotate 360º like a tiny propeller

Basal body

Part of flagellum: Attached to cell wall & cell membrane; composed of the rod and rings

Four rings

Gram-negative bacteria have how many rings?

Two rings

Gram-positive bacteria have how many rings?

Taxis

Move towards or away from a stimulus

Chemotaxis

Move towards or away from a chemical signal

Postive Chemotaxis

Move towards favorable stimulus (attractant)

Negative Chemotaxis

Move away from harmful compound (repellant)

Phototaxis

Move towards or away from light

Monotrichous

Single flagellum in one pole

Lophotrichous

Several flagella in one pole

Amphitrichous

Several flagella on both sides

Peritrichous

Flagella is dispersed all over the surface of the bacteria

Atrichous

Absence of flagellum

Periplasmic Flagella (Axial Filament/Endoflagella)

Found in spirochetes (corkscrew-shaped bacterium). Internal flagellum is located between the cell wall and the outer sheath. Anchored at one end of the spirochete in the cytoplasmic cylinder. Imparts a twisting or flexing motion to the cell

Motility Test

True Motility: cells flip, dart or wobble. Non Motile: cells jiggle about at one place

Fimbriae

Composition: fimbrillin protein. Structures located at the pole or spread throughout the surface of the bacterium. Functions: Cell-to-Cell and Host Attachment/Adhesion. Biofilm formation: Bacterial aggregates that clump together to cover the surface epithelium, Found in gram-positive and gram-negative bacteria

Pili

Composition: pilin protein. Elongated tubular structure composed of the protein pilin. Longer than fimbriae. Functions: As sex pilus: Conjoins two bacteria together for transfer of bacterial DNA from one cell to another. As ordinary pilus: Aids in attachment to the host surface. Found in gram-negative bacteria

Cell Envelope

Boundary of a bacterium. Composed of a 2-layered and tightly bound stack of cell wall and cell membrane

Cell Wall

Multi-layered structure external to the cell membrane. Present in most bacteria, with some exceptions (i.e., Mycoplasma). Functions: Provide structure to maintain bacterial shape, Osmotic protection, Anchors flagella, Site of action of certain antibiotics (i.e., penicillin). Composed of a lattice of peptidoglycans

Gram-Positive Bacteria

Have a thicker peptidoglycan or murein layer. Have a single layer of cytoplasmic membrane. Its cell wall features negatively charged teichoic acids. Provide strength and elasticity to the cell wall. Bear antigen determinants that can elicit an immune response, which are used to identify the specific bacteria

Gram-negative Bacteria

Thinner as compared to Gram (+) bacteria. Have two cytoplasmic membranes: Inner and Outer. Their cell walls have a periplasmic space, porins and lipopolysaccharide or endotoxins. The peptidoglycan layer of gram negative bacteria are located within the periplasmic space

Periplasmic Space

Contains the following: DNA cells, Hydrolytic enzymes, Amino acids, Hydrolases

Porins

Allows passage of mid-sized molecules (ie. glucose) as well as: Nucleotides, Peptides, Amino acids, Vitamin B12, Iron

Liposaccharide (Endotoxins)

Found in outer membrane of gram-negative bacteria. Responsible for the toxic effect it has on its host

Gram-positive

Stains purple on Gram-stain. Flagellum has 1 pair of rings. Thick peptidoglycan layer. Single cellular (inner) membrane. With Teichoic acids: Bears antigenic determinants, Regulate cation movement, No need for porins

Gram-negative

Stains reddish-pink on gram-stain. Flagellum has 2 pairs of rings. Thin peptidoglycan layer. Has outer and inner membranes: Endotoxins (lipopolysaccharides), porin protein on its outer membrane, Has periplasmic space

Liposaccharides (Endotoxin)

Composed of O-antigen or O-Polysaccharide which is used in identifying these organisms. Has a Core Polysaccharide and Lipid A

Lipid A

It can induce inflammation and lead to anaphylactic shock, disseminated intravascular coagulation (DIC), and death of patients

Mycoplasma

A bacterium with no cell wall. Contains sterols in the plasma membrane. In gram stain, appears clear (not visible when viewed under microscope)

Mycobacterium Tuberculosis and Nocardia

Its cell wall is 60% mycolic acid (cord factor) and 40% peptidoglycans. Acid fast cells because they can resist decolorization by acids during laboratory staining procedures

Cell Membrane

Composed of phospholipid bilayers where various globular proteins are embedded. Functions: Selective barrier and help in the active transport of solutes. Channels the release of metabolic products into the extracellular environment. It is where electron transport and oxidative phosphorylation in bacteria occu. Secretions of enzymes and toxins

Mesosomes

Internal folds or invaginations. Participate in cellular respiration and cell division

Cytoplasm

The amorphous matrix within the cellular membrane that contains 70-85% water, protein, carbohydrates, lipids, and inorganic ions. Functions: Site for biochemical and synthetic activities. Its water acts as a solvent for a complex mixture of nutrients. The components of its pool serve as a building block and source of energy

Nucleoid

Single-stranded DNA. Directs activity of cell. Haploid

Plasmids

May or may not be present. Circular pieces of DNA that are non-essential to bacterial growth and metabolism. Can be inserted in bacterial chromosomes and confer protective traits such as drug resistance, production of toxins and enzymes, allowing them to be more virulent

Ribosomes

70S. Site of protein synthesis

Inclusion (Granules)

Glycogen, lipids, phosphates. Acts as a storage for nutrients: Metachromatic granules, Polysaccharide granules, Lipid inclusions, Sulfur granules

Bacterial Endospore

Some bacteria, like Bacillus and Clostridium, have the ability to form spores, both are Gram-positive. Spore Formation - more of a means of survival than reproduction. High calcium dipicolinate found in their core makes them highly resistant to heat, drying, freezing, and long term survival. Location: central, terminal, subterminal

Endospore Formation

Starts when the bacterium is placed in an unfavorable environment like places with decreased water and nutrients. In the process, the cell undergoes transformation leading to the development and release of spores. One vegetative cell produces only one spore

Endospore Germination

Breaking of dormancy. Takes place when spores are placed in a favorable environment. The presence of water and specific chemicals acts as an environmental stimuli. Hydrolytic enzymes break the surrounding layers of the endospore. Spore swells and releases the vegetative cell

Aerobic

Needs oxygen to grow. Can use oxygen in their metabolism and possess enzymes needed to process toxic oxygen

Anaerobic

Does not require oxygen. Inhabit parts of the body that are oxygen-free (e.g. large intestine). Oxygen is toxic for their growth

Facultative Anaerobe

Grows with or without oxygen. Metabolize by aerobic respiration if oxygen is present. Adapts to anaerobic mode of metabolism if oxygen is absent

Micro-aerophilic

Requires oxygen at a low level. Do not grow at normal concentration of atmospheric oxygen but require only a small amount in metabolism

Aerotolerant

They do not use oxygen but survive its presence. Not harmed by oxygen because they contain an alternate mechanism for breaking down peroxide and superoxide

Capnophile

Grows best at higher carbon dioxide concentration (5-10%) and low amounts of oxygen

Gram-positive

Identify if gram-negative, gram-positive, neither, or both: Teichoic acids

Both

Identify if gram-negative, gram-positive, neither, or both: Cytoplasm

Gram-negative

Identify if gram-negative, gram-positive, neither, or both: Periplasmic space

Gram-negative

Identify if gram-negative, gram-positive, neither, or both: Lipopolysaccharides

Both

Identify if gram-negative, gram-positive, neither, or both: Small Ribosomes

Neither

Identify if gram-negative, gram-positive, neither, or both: Histones

Both

Identify if gram-negative, gram-positive, neither, or both: Cell wall

Both

Identify if gram-negative, gram-positive, neither, or both: Nucleiod

Gram-positive

Identify if gram-negative, gram-positive, neither, or both: Thick peptidoglycan

Neither

Identify if gram-negative, gram-positive, neither, or both: Endoplasmic reticulum

Gram-positive

Identify if gram-negative, gram-positive, neither, or both: Lipoteichoic acids

Both

Identify if gram-negative, gram-positive, neither, or both: Binary fission

Gram-negative

Identify if gram-negative, gram-positive, neither, or both: Thin peptidoglycan

Both

Identify if gram-negative, gram-positive, neither, or both: Inner cellular membrane

Both

Identify if gram-negative, gram-positive, neither, or both: Prokaryote

Neither

Identify if gram-negative, gram-positive, neither, or both: Mitochondria

Gram-positive

Identify if gram-negative, gram-positive, neither, or both: Stains purple

Both

Identify if gram-negative, gram-positive, neither, or both: N-acetylmuramic acid

Neither

Identify if gram-negative, gram-positive, neither, or both: Nucleus

Gram-negative

Identify if gram-negative, gram-positive, neither, or both: Lipid A