Applied Microbiology 3nd lecture: Chapter 4

Characteristics of Cells and Life Prokaryotic Cells Characteristics of Cells and Life All living things (single and multicellular) are made of cells that share some common characteristics: - basic shape – spherical, cubical, cylindrical - internal content – cytoplasm, surrounded by a membrane DNA chromosome(s), ribosomes, metabolic capabilities Two basic cell types: eukaryotic and prokaryotic

Characteristics of Cells Prokaryotic Cells Characteristics of Cells Eucaryotic cells: animals, plants, fungi, and protists contain double-membrane bound nucleus with DNA chromosomes contain membrane-bound organelles that compartmentalize the cytoplasm and perform specific functions Procaryotic cells: bacteria and archaea - no nucleus or other membrane-bound organelles

Characteristics of Life Prokaryotic Cells Characteristics of Life What is life ? Growth and development Reproduction and heredity – genome composed of DNA packed in chromosomes; produce offspring sexually or asexually Metabolism – chemical and physical life processes Movement and/or irritability – respond to internal/external stimuli; self-propulsion of many organisms Cell support, protection, and storage mechanisms – cell walls, vacuoles, granules and inclusions Transport of nutrients and waste

Prokaryotic Profiles: Bacteria and Archaea Prokaryotic Cells Prokaryotic Profiles: Bacteria and Archaea

Prokaryotic Profiles: Bacteria and Archaea Prokaryotic Cells Prokaryotic Profiles: Bacteria and Archaea

Prokaryotic Cells External Structures - Appendages two major groups of appendages: Motility – flagella and axial filaments (periplasmic flagella) Attachment or channels – fimbriae and pili - Glycocalyx – surface coating

External Structures - Flagella Prokaryotic Cells External Structures - Flagella 3 parts: 1. filament – long, thin, helical structure composed of protein flagellin 2. hook- curved sheath 3. basal body – stack of rings firmly anchored in cell wall Rotates 360o Number and arrangement of flagella varies: monotrichous, lophotrichous, amphitrichous, peritrichous -> Functions in motility of cell through environment

External Structures - Flagella Prokaryotic Cells External Structures - Flagella Gram-negative Gram-positive

External Structures – Flagella Arrangements Prokaryotic Cells External Structures – Flagella Arrangements Monotrichous – single flagellum at one end Lophotrichous – small bunches arising from one end of cell Amphitrichous – flagella at both ends of cell Peritrichous – flagella dispersed over surface of cell; slowest

External Structures – Flagella Arrangements Prokaryotic Cells External Structures – Flagella Arrangements Monotrichous Lophotrichous Peritrichous Amphitrichous

External Structures – Operation of Flagella Prokaryotic Cells External Structures – Operation of Flagella counterclockwise –> results in smooth linear direction – run clockwise -> cell stops and tumbles

External Structures – Flagella Function Prokaryotic Cells External Structures – Flagella Function Guide bacteria in a direction in response to external stimulus: -> chemical stimuli – chemotaxis; positive and negative -> light stimuli – phototaxis Signal sets flagella into rotary motion clockwise or counterclockwise: -> counterclockwise – results in smooth linear direction – run -> clockwise - tumbles

External Structures – Chemotaxis Prokaryotic Cells External Structures – Chemotaxis

External Structures – Axial Filaments Prokaryotic Cells External Structures – Axial Filaments Periplasmic, internal flagella, enclosed between cell wall and cell membrane of spirochetes Produce cellular motility by contracting and imparting twisting or flexing motion

External Structures – Other Appendages: Fimbriae Prokaryotic Cells External Structures – Other Appendages: Fimbriae Fine, proteinaceous, hairlike bristles from the cell surface Function in adhesion to other cells and surfaces -> do not provide locomotion -> pathogens use it to attach tightly to epithelial cells -> infection

External Structures – Other Appendages: Pili Prokaryotic Cells External Structures – Other Appendages: Pili Rigid tubular structure made of pilin protein Found only in Gram negative cells Function to join bacterial cells for partial DNA transfer called conjugation -> sex pili

External Structures – Glycocalyx Prokaryotic Cells External Structures – Glycocalyx Coating of molecules external to the cell wall, -> made of sugars and/or proteins Two types: -> slime layer - loosely organized and attached -> capsule - highly organized, tightly attached Functions: -> protect cells from dehydration and nutrient loss -> inhibit killing by white blood cells by phagocytosis contributing to pathogenicity -> attachment - formation of biofilms

External Structures – Glycocalyx -> Biofilms Prokaryotic Cells External Structures – Glycocalyx -> Biofilms Staphylococcus aureus

Prokaryotic Cells The Cell Envelope -> External covering outside the cytoplasm -> Composed of two basic layers: cell wall and cell membrane -> Maintains cell integrity -> Two generally different groups of bacteria demonstrated by Gram stain: Gram-positive bacteria: thick cell wall composed primarily of peptidoglycan and cell membrane Gram-negative bacteria: outer cell membrane, thin peptidoglycan layer, and cell membrane

Prokaryotic Cells The Cell Envelope

Prokaryotic Cells The Cell Envelope

The Cell Envelope: Cell Wall Prokaryotic Cells The Cell Envelope: Cell Wall -> Determines cell shape, prevents lysis (bursting) or collapsing due to changing osmotic pressures Peptidoglycan is primary component: unique macromolecule composed of a repeating framework of long glycan chains cross-linked by short peptide fragments

The Cell Envelope: Cell Wall Prokaryotic Cells The Cell Envelope: Cell Wall Peptidoglycan

The Cell Envelope: Gram-Positive Cell Wall Prokaryotic Cells The Cell Envelope: Gram-Positive Cell Wall Thick, homogeneous sheath of peptidoglycan -> 20-80 nm thick -> includes teichoic acid and lipoteichoic acid: function in cell wall maintenance and enlargement during cell division; move cations across the cell envelope; stimulate a specific immune response

The Cell Envelope: Gram-Negative Cell Wall Prokaryotic Cells The Cell Envelope: Gram-Negative Cell Wall -> Composed of an outer membrane and a thin peptidoglycan layer -> Protective structure while providing some flexibility and sensitivity to lysis -> Periplasmic space surrounds peptidoglycan -> Outer membrane is similar to cell membrane bilayer structure - outermost layer contains lipopolysaccharides and lipoproteins (LPS) > endotoxin that may become toxic when released during infections > may function as receptors and blocking immune response contains porin proteins in upper layer – regulate molecules entering and leaving cell Bottom layer composed of phospholipids and lipoproteins

Prokaryotic Cells The Cell Envelope: Gram-Negative Cell Wall Porin (channel for small molecule passage).

The Cell Envelope: Comparison of Cell Walls Prokaryotic Cells The Cell Envelope: Comparison of Cell Walls

The Cell Envelope: Comparison of Gram + and Gram- Prokaryotic Cells The Cell Envelope: Comparison of Gram + and Gram-

Prokaryotic Cells The Gram Stain -> Differential stain that distinguishes cells with a Gram-positive cell wall from those with a Gram-negative cell wall Gram-positive - retain crystal violet and stain purple Gram-negative - lose crystal violet and stain red from safranin counterstain -> Important basis of bacterial classification and identification -> Practical aid in diagnosing infection and guiding drug treatment

Prokaryotic Cells The Gram Stain

Prokaryotic Cells Atypical Cell Walls Some bacterial groups lack typical cell wall structure i.e. Mycobacterium and Nocardia Gram-positive cell wall structure with lipid mycolic acid (cord factor) -> pathogenicity and high degree of resistance to certain chemicals and dyes -> basis for acid-fast stain used for diagnosis of infections caused by these microorganisms Some have no cell wall i.e. Mycoplasma -> cell wall is stabilized by sterols -> pleomorphic (variations in shape)

Degradation of Cell Walls Prokaryotic Cells Degradation of Cell Walls Lysozyme cleaves Peptidoglycan Penicillin inhibits enzyme responsible for construction of peptidoglycan Gram-positive cell exposed to one of these agents -> cell wall completely loosened -> protoplast Gram-negative cell exposed to one of the agents -> peptidoglycan loosened but outer membrane retained -> spheroplast

Prokaryotic Cells Cell Membrane Phospholipid bilayer with embedded proteins – fluid mosaic model Functions in: -> providing site for energy reactions, nutrient processing, and synthesis -> transport into and out of the cell

Bacterial Internal Structures Prokaryotic Cells Bacterial Internal Structures Cell cytoplasm: -> dense gelatinous solution of sugars, amino acids, and salts -> 70-80% water serves as solvent for materials used in all cell functions

Bacterial Internal Structures Prokaryotic Cells Bacterial Internal Structures Chromosome -> single, circular, double-stranded DNA molecule that contains all the genetic information required by a cell -> DNA is tightly coiled around a protein, aggregated in a dense area called the nucleoid.

Bacterial Internal Structures Prokaryotic Cells Bacterial Internal Structures Plasmids -> small circular, double-stranded DNA -> free or integrated into the chromosome -> duplicated and passed on to offspring -> not essential to bacterial growth and metabolism -> may encode antibiotic resistance, tolerance to toxic metals, enzymes and toxins -> used in genetic engineering- readily manipulated and transferred from cell to cell

Bacterial Internal Structures Prokaryotic Cells Bacterial Internal Structures Ribosomes -> made of 60% ribosomal RNA and 40% protein -> consist of two subunits: large and small -> procaryotic differ from eucaryotic ribosomes in size and number of proteins -> site of protein synthesis -> present in all cells

Bacterial Internal Structures Prokaryotic Cells Bacterial Internal Structures Inclusions and granules -> intracellular storage bodies -> vary in size, number and content -> Bacterial cell can use them when environmental sources are depleted. examples: glycogen, poly-b-hydroxybutyrate, gas vesicles for floating, sulfur and phosphate granules (metachromatic granules)

Bacterial Internal Structures Prokaryotic Cells Bacterial Internal Structures Endospores -> inert, resting, cells produced by some G+ genera: Clostridium, Bacillus and Sporosarcina -> have a 2-phase life cycle: - vegetative cell – metabolically active and growing endospore – when exposed to adverse environmental conditions; capable of high resistance and very long - term survival

Bacterial Internal Structures Prokaryotic Cells Bacterial Internal Structures Endospores sporulation -formation of endospores -> hardiest of all life forms -> withstands extremes in heat, drying, freezing, radiation and chemicals -> not a means of reproduction germination- return to vegetative growth

Bacterial Internal Structures Prokaryotic Cells Bacterial Internal Structures

Bacterial Internal Structures Prokaryotic Cells Bacterial Internal Structures Endospores: -> Resistance linked to high levels of calcium and dipicolinic acid -> Dehydrated, metabolically inactive -> thick coat -> Longevity verges on immortality - 25,250 million years. -> Resistant to ordinary cleaning methods and boiling -> Pressurized steam at 120oC for 20-30 minutes will destroy -> some pathogens make spores -> B. anthraces, C. tetani

Bacterial Shapes, Arrangements, and Sizes Prokaryotic Cells Bacterial Shapes, Arrangements, and Sizes Variety in shape, size, and arrangement but typically described by one of three basic shapes: -> coccus - spherical -> bacillus – rod coccobacillus – very short and plump vibrio – gently curved -> spirillum - helical, comma, twisted rod, spirochete – spring-like

Bacterial Shapes, Arrangements, and Sizes Prokaryotic Cells Bacterial Shapes, Arrangements, and Sizes Bacterial shapes

Bacterial Shapes, Arrangements, and Sizes Prokaryotic Cells Bacterial Shapes, Arrangements, and Sizes

Bacterial Shapes, Arrangements, and Sizes Prokaryotic Cells Bacterial Shapes, Arrangements, and Sizes Arrangement of cells is dependent on pattern of division and how cells remain attached after division: cocci: -> singles -> diplococci – in pairs -> tetrads – groups of four -> irregular clusters -> chains -> cubical packets bacilli: -> palisades

Bacterial Shapes, Arrangements, and Sizes Prokaryotic Cells Bacterial Shapes, Arrangements, and Sizes Arrangement of Cocci

Bacterial Shapes, Arrangements, and Sizes Prokaryotic Cells Bacterial Shapes, Arrangements, and Sizes Dimensions of Bacteria

Classification Systems in the Prokaryotes Prokaryotic Cells Classification Systems in the Prokaryotes -> Microscopic morphology -> Macroscopic morphology – colony appearance -> Physiological / biochemical characteristics -> Chemical analysis -> Serological analysis -> Genetic and molecular analysis - G + C base composition - DNA analysis using genetic probes - Nucleic acid sequencing and rRNA analysis

Classification Systems in the Prokaryotes Prokaryotic Cells Classification Systems in the Prokaryotes Taxonomy Based on Bergey’s Manual -> Bergey’s Manual of Determinative Bacteriology – five volume resource covering all known procaryotes -> classification based on genetic information –phylogenetic -> two domains: Archaea and Bacteria -> five major subgroups with 25 different phyla

Classification Systems in the Prokaryotes Prokaryotic Cells Classification Systems in the Prokaryotes Major Taxonomic groups: Domain Archaea – primitive, adapted to extreme habitats and modes of nutrition Domain Bacteria – Phylum Proteobacteria – Gram-negative cell walls Phylum Firmicutes – mainly Gram-positive with low G + C content Phylum Actinobacteria – Gram-positive with high G + C content

Classification Systems in the Prokaryotes Prokaryotic Cells Classification Systems in the Prokaryotes Diagnostic Scheme for Medical Use: Uses phenotypic qualities in identification -> restricted to bacterial disease agents -> divides based on cell wall structure, shape, arrangement, and physiological traits

Classification Systems in the Prokaryotes Prokaryotic Cells Classification Systems in the Prokaryotes Gram-positive Pathogens Clostridium botulinum. CDC. C. tetani -> tetanus Bacillus anthracis Staphylococcus aureus Corynebacterium diphtheriae

Classification Systems in the Prokaryotes Prokaryotic Cells Classification Systems in the Prokaryotes Gram-negative Pathogens Neisseria meningitis Yersinia pestis B. Burgdorferi Borrellia -> Lyme disease

Prokaryotic Cells Classification Systems in the Prokaryotes Pathogen with no cell wall Mycoplasma “fungus-form” -> pneumonia The smallest bacteria - 0.2 micrometers

Classification Systems in the Prokaryotes Prokaryotic Cells Classification Systems in the Prokaryotes The smallest Bacteria – Nanobes or Nanobacteria -> Size: 0.05 – 0.2 μm -> first isolated in blood serum -> grow in cultures -> have cell walls, protein, nucleic acids -> isolated from sandstone from ocean (100-170°, embedded in minerals) Not clear if: -> they are similar to first microbe on earth -> or just artifacts, part of cells since functional cells need to be at least 0.13μm

Classification Systems in the Prokaryotes Prokaryotic Cells Classification Systems in the Prokaryotes Species and Subspecies in Bacteria Species –a collection of bacterial cells which share an overall similar pattern of traits in contrast to other bacteria whose pattern differs significantly Strain or variety – microbes that belong to the same species but are further subdivided based on unique chemicals found either on the cell surface, or being secreted as exotoxins. For example, there is a difference between the type of toxin produced by the strain of E.coli in the U.S., and the strain found in water in Mexico Type – a subspecies that can show differences in antigenic makeup (serotype or serovar), susceptibility to bacterial viruses (phage type) and in pathogenicity (pathotype)

Classification Systems in the Prokaryotes Prokaryotic Cells Classification Systems in the Prokaryotes Prokaryotes with unusual characteristics Cyanobacteria (blue-green algae) Photosynthetic bacteria - use photosynthesis, can synthesize required nutrients from inorganic compounds Formed O2 in the earth’s atmosphere Gram-negative cell walls

Classification Systems in the Prokaryotes Prokaryotic Cells Classification Systems in the Prokaryotes Prokaryotes with unusual characteristics Green and purple sulfur bacteria contain photosynthetic pigment bacteriochlorophyll do not give off oxygen as a product of photosynthesis Live in sulfur springs

Classification Systems in the Prokaryotes Prokaryotic Cells Classification Systems in the Prokaryotes Prokaryotes with unusual characteristics - Pathogens Rickettsias Very tiny, Gram-negative bacteria Most are pathogens that alternate between mammals and fleas, lice or ticks. Rickettsia rickettisii – Rocky Mountain spotted fever Rickettsia prowazekii – epidemic typhus Coxiella burnetti – Q fever

Classification Systems in the Prokaryotes Prokaryotic Cells Classification Systems in the Prokaryotes Prokaryotes with unusual characteristics - Pathogens Chlamydias Tiny Chlamydia trachomatis – severe eye infection and one of the most common sexually transmitted diseases Chlamydia psittaci – ornithosis, parrot fever Chlamydia pneumoniae – lung infections

Prokaryotic Cells Archaea -> Constitute third Domain Archaea -> Seem more closely related to Domain Eukarya than to bacteria -> Have unique membrane lipids (ether lipids) and cell wall construction -> Live in the most extreme habitats in nature, extremophiles -> Adapted to heat, salt, acid pH, pressure and atmosphere Includes: methane producers, hyperthermophiles, extreme halophiles, and sulfur reducers

Prokaryotic Cells Archaea Thermophiles growing in Yellowstone hot springs. Halophiles growing in Owens Lake, California.