Cell Size and Structure: Microbiology

• Bacteria is a lower protist (prokaryotic).
• Bacteria cells do not have a nucleus.
• Bacteria is an intermediate organism between viruses.
• Bacteria cells possess nucleoid with DNA.
• Bacteria genome, or chromosome, is a single, circular molecule of double-stranded DNA, lacking a nuclear membrane.

Reproduction

• Bacteria reproduce/divide by binary fission.
• Bacteria can replicate extracellularly.
• Bacteria may contain extrachromosomal elements called plasmids.
• Bacteria cell division by binary fission is asexual reproduction.
• Bacteria transfer their genetic infomration by conjugation, transduction, and transformation.

Eukaryotes vs Prokaryotes

• Eukaryotes are algae (besides blue green algae), protozoa, and fungi.
• Prokaryotes are bacteria and blue green algae.
• Virus is NOT a cell.
• Eukaryotes exhibit chromosome with true nucleus with a nuclear membrane.
• A eukaryotic cell has a true nucleus with multiple chromosomes surrounded by a nuclear membrane.
• Eukaryotes' DNA is complexed with histone proteins.

Table 2.1 Characteristics

• Bacteria have muramic acid in their cell wall, and rigid cell wall.
• Bacteria are capable of free growth, has both DNA and RNA present, and the reproduce essentially by binary fission.
• Bacteria are susceptible to tetracycline 30S.

Svedberg

• Theodor Svedberg won the 1926 Nobel Prize for chemistry for his work in colloid chemistry.
• Svedberg is a unit of measurement of the velocity of sedimentation, and the molecular weight of proteins
• Prokaryotes have 70S ribosomes.
• 70S ribosomes are composed of 50S and 30S subunits
• Eukaryotes have 80S ribosomes
• A prokaryotic bacterial genome that contains a single, circular molecule of double-stranded DNA, lacking a nuclear membrane (smaller, single or multiple circular DNA molecules called plasmids)
• Eukaryotes are fungi, protozoa and humans.

Eubacteria

• Eubacteria are prokaryotes.
• Eubacteria are different than archae bacteria
• Eubacteria comprise vast majority of human pathogens.

General information

• Microorganisms are algae, protozoa, fungi, bacteria, and viruses.
• Kingdom protists are bacteria, fungi and protozoa.
• Bacteria are a single cell (unicellular) by being unicellul
• 1cm = 10mm
• 1mm = 1000 micro.m = 1 million nano m

Morphology

• Bacteria are classified by their shape into three basic groups.
• The shape of a bacterium is determined by its rigid cell wall.
• Bacteria classes are cocci, bacilli, and spiral
• cocci = spherical
• bacilli = rod-shaped
• spiral = helical
• Some bacteria with variable shapes, appearing both as cocci and bacillary forms, are called pleomorphic.
• Bacteria sizes range from about 0.2 to 2.0 micro.meter.
• Bacteria's arrangement can be pairs (diplococci), chains (streptococci), grape-like clusters (staphylococci), and/or angled pairs or palisades (corynebacteria).

Gram Staining

• Bacteria is classified into two subgroups, gram-positive and gram-negative.
• The classification is determined by the staining characteristics of their cell walls.
• Gram stain was first developed by a danish physician, Christian Gram.
• Gram-positive (purple)
• Gram-negative (pink)
• Gram-positive bacteria are more susceptible to penicillins.

structure

• Bacteria have a rigid cell wall protecting a fluid protoplast that has a cytoplasmic membrane
• Protoplast is composed of cytoplasmic membrane, cytoplasm, nucleus and cell organ.
• Structure external to the self are flagella, fimbriae and pili, glycocalyx (slime layer), and capsule.
• Bacterial DNA comprises a single, supercoiled, circular chromosome that contains about 2000 genes.
• Periplasmic space is between the outer membrane and the cytoplasmic membrane of Gram-negative bacteria.

Flagella

• Flagella are whip-like filaments that act as propellers to guide bacteria.
• Flagella are composed of many subunits of flagellin proteins.
• monotrichous: single polar flagellum
• amphitrichous: single flagellum attached to each end
• lophotrichous: tufts of flagella at one or both ends
• peritrichous: flagella all over the outer surface

Pili and Fimbriae

• Fimbriae and pili are fine, hair-like filaments (shorter than flagella)
• Pili are found mainly in gram-negative organisms
• Pili mediate the adhesion of bacteria to receptors on the human cell surface, which is a necessary step for infection.
• A pilus can be a sex pilus, which is a specialized type of pilus forms the attachment between the male (donor) and the female (recipient) bacteria during conjugation, when genes are transferred from one bacterium to another.

Glycocalyx

• Glycocalyx is a polysaccharide coating that covers the teeth, heart valves and many bacteria.
• Glycocalyx allows the bacteria to adhere
• Glycocalyx helps defends against desiccation

Capsule

• Capsule is an amorphous, gelatinous layer
• 3 types of bacterial capsules exist. It sometimes contains polysaccharide or a protein (e.g. Bacillus anthracis: anthrax disease)
• Sugar components in the polysaccharide vary and frequently determine the serological type within a species.
• Capsules mediates human tissues or prosthesis such as dentures or implants because it has adhesion of bacteria
• Capsules correlates hinders/inhibits with virulence.
• Laboratory identification of organisms will swell greatly in presence of antiserum against the capsule.
• The capsule of S. pneumonia has antigen and requires vaccines.

Cell Wall

• Cell wall offers rigidity to the bacterial cell.
• There are multilayered structures outside inside the cell.
• Peptidoglycan is a component of the cell wall.
• Cell wall is made of peptidoglycan and is covered by an outer membrane (in G-ve).
• The term 'peptidoglycan' is derived from the peptides and the glycan.
• Cell walls of Gram-positive and Gram-negative bacteria have important structural and chemical differences
• Gram-positive and Gram-negative bacteria both have peptidoglycan layers.
• Peptidoglycan layer is is much thicker in gram-positive bacteria.
• Gram-negative organisms possess have a complex outer membrane composed of lipopolysaccharide (LPS), lipoprotein and phospholipid.
• Gram-negative bacteria contain porins. Porins transports hydrophilic molecules in and out of the organism.
• Lies between the outer outer membrane and the cytoplasmic membrane in gram-negative bacteria cells.
• Gram-negative bacteria use their LPS to produce endotoxins.
• Mycolic acids are found in the cell walls of some contain lipids (e.g. Mycobacterium tuberculosis).
• The mycolic acids cannot be gram-stained, and hence is called called acid-fast

###LPS

• LPS consists of O antigen, core and lipid A, embedded in the outer membrane
• Bacteria with defective cell walls
• Have mycoplasmas which do not possess a cell wall and is usually l-forms
• L-forms are usually produced in the laboratory.
• Bacterial with walls that are non-existant do not have tolerance to hypertonic media.

Cytoplasmic membrane

• Cytoplasmic membranes lies just inside just insite
• Cytoplasmic membrane consists of a phospholipid bilayer similar in appearance to that found in eukoryotic cells
• Lipids in the two have differing molecular weight.
• Eukaryotic membranes sterols, prokaryotes generally no.

Cytoplasmic membrane functions

• It is used for active transport and diffusion of molecules.
• It can be used for electron and oxidative phosphorylatoin.
• It can store enzymes
• It can support proteins via heads.

Mesosome

• Mesosomes are convoluted invagination of cytoplasmic
• Functions to assist with division of DNA

Cytoplasm

• Composed of nucloid region of an inner layer.
• contains ribosomes, nutrient granules, metabolites and various ions.
• nucleoid material is bacteria DNA containing single celled supercoiled
• it is also Hapliod.

DNA

• Is supercoiled and can used as an approximate Haploid
• DNA is semiconservative.

Ribosomes

• Prokotes consists of 50S and 30S
• Antibiotics are used to inhibit some functions.

Cytoplasmic

• Contain inclusions to help source stored energy, polymetaphosphate
• Bacterial spores are used for adverse conditions (bacillus anthracis).
• It contains also agent anthrax as part of the genius.

Spore Formations

• bacterial forms grow as vegetative cells
• Dna is condensed and center aligns. Vegetative cell converts ot mother.
• Dipicolinc aide, caiclium enters to form layers a protein coat, then lysic is formed in enzyme.
• It can be activated to form the call back again as a step of gernmination

Spore

• It cannot be metabolized and becomes metabolically
• it can be resistant due to the outer coat that can take high concentration
• it has to degraded enzymatically for activation.

Bacterial Spores formation

• Is when the cell replicates in adverse conditional
• Contains many of the components in cell memebrane.

Clinical Relevence

• Can be sterilize with many things.

Taxonomy

• diagnostic microbiology is the study of epidemdiology
• Phenotypic is an study of the morphology
• Genotypic is the is DNA structure with C2G to C4C
• recent research indicates that endogenous bacterial habitats in humans, including the oral cavity

Test your knowledge of cell sizes and structures in microbiology. Questions cover cell diameter, bacteria vs. yeast sizes, flagellar arrangements like monotrichous and amphitrichous, and external cell structures. Identify microorganisms based on their size and characteristics.