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1 Characteristics of microbes Viruses Not cells; contain either RNA or DNA in envelope; can only multiply in living cells. Major groups of microorganisms.

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Presentation on theme: "1 Characteristics of microbes Viruses Not cells; contain either RNA or DNA in envelope; can only multiply in living cells. Major groups of microorganisms."— Presentation transcript:

1 1 Characteristics of microbes Viruses Not cells; contain either RNA or DNA in envelope; can only multiply in living cells. Major groups of microorganisms Bacteria Unicellular; procaryotic; rigid cell wall; absorb nutrients. Archaebacteria; eubacteria Archaebacteria Non-peptidoglycan cell walls Have unusual metabolic capabilities. Live in extreme environments. Methanogens, halophiles and thermoacidophiles.

2 2 Characteristics of microbes Fungi Either uni- or multicellular; eucaryotic; rigid cell walls; absorb nutrients. Major groups of microorganisms 2 Protozoa Single celled; eucaryotic; lack rigid cell wall; ingest food. Algae Either uni- or multicellular; eucaryotic; rigid cell walls; chlorophyll; absorb nutrients.

3 3 Structure/function of eubacteria Size, shape and arrangement Diameter Length Ave m up to 500 m m wide m long (E. coli ) Spherical Rods Spiral coccus (sing.) cocci (pl.) meaning berries. bacillus (sing.) bacillus (pl.) meaning little staffs. spirullum (sing.) spirilla (pl.) Pleomorphyvariety of shapes in a species

4 4 Structure/function of eubacteria Size, shape and arrangement 2

5 5 Structure/function of eubacteria Size, shape and arrangement 3

6 6 Structure/function of eubacteria Ultrastructure Cell wall

7 7 Structure/function of eubacteria Cell wall Ultrastructure 2 Rigid, strong structure; gives and maintains shape % of dry weight of the cell. Usually essential for cell division. A barrier to some substances. Not homogeneous structures; depending on species, layered with different substances which have different thicknesses.

8 8 Structure/function of eubacteria Peptidoglycan (a.k.a. murein) Ultrastructure 3 Comprises N-acetylglucosamine, N-acetylmuramic acid and tetrapeptides. Peptidoglycan chains are cross-linked at the tetrapeptide units. Autolysin opens the network for addition of new polymer. Shape determining part of the wall. Insoluble, porous polymer of great strength and rigidity.

9 9 Structure/function of eubacteria Ultrastructure 3

10 10 Structure/function of eubacteria There are 2 types of cells wall in eubacteria Ultrastructure 4 Gram stain differently Differences in the layering and presence of outer membrane (in G -) explains the difference in Gram reaction and pathogencity.

11 11 Structure/function of eubacteria The G(+) cell wall Ultrastructure 5 Peptidoglycan content 50%cf. G(-) 10% walls of G(+) bacteria appear thicker. Contains techoic acid (may aid in the transport of cations).

12 12 Structure/function of eubacteria The G(-) cell wall Ultrastructure 5 More complex; has outer membrane covering a thin layer of peptidoglycan. Outer membrane: Contains lipolysaccharides (lipid portion causes toxic effects in infected animals).

13 13 Structure/function of eubacteria Cytoplasmic membrane Ultrastructure 5 Composition: Phospholipids % Proteins %

14 14 Structure/function of eubacteria Cytoplasmic membrane 2 Ultrastructure 6 A site of specific enzyme activity, transport of molecules in and out of the cell, and invaginations participate in cell metabolism and replication. Some processes essential to the cell are located here. A barrier to most water-soluble molecules, and is more selective than the cell wall. Permeases transport small molecules into the cell. Also contains various enzymes for energy production and synthesis of cell wall. Photosynthetic bacteria or those with metabolisms based on gas exchange have elaborate intracellular extensions of the cytoplasmic membrane. This infolding increases the area for light pigments or gas exchange.

15 15 Structure/function of eubacteria Ultrastructure Cytoplasmic area

16 16 Structure/function of eubacteria Cytoplasmic area Ultrastructure 6 80% water with nucleic acids, proteins, carbohydrates, lipids, inorganic ions, many low-molecular weight compounds and particles with various functions. Ribosomes. Free in cytoplasm, not membrane-bound. Cell inclusions (insoluble chemical substances accumulated) e.g. metachromatic granules (a.k.a volutin; a reserve of inorganic phosphate). Lipids e.g. poly- -hydroxybutyrate; reserve carbon and energy source. Sulfur: H 2 S-oxidizing bacteria. Polysaccharides e.g. glycogen and starch; reserve energy sources.

17 17 Structure/function of eubacteria Ultrastructure Nuclear area

18 18 Structure/function of eubacteria Nuclear area Ultrastructure 6 No nuclear membrane. Nuclear material found near the center of the cell and is attached to the mesosome-cytoplasmic membrane. Total nuclear material = nucleoid; consist of a single circular chromosome.

19 19 Structure/function of eubacteria Ultrastructure Flagella

20 20 Flagella(e) Ultrastructure 6 Thin, helical, hair-like filaments; extends from the cytoplasm through the cell wall. Observable in stained specimens. Propels the cell. Up to 100 m min cell lengths min -1 cf. the cheetahs top speed of 1500 body lengths min -1. Peritrichous flagellation Polar flagellation: monotrichous; lophotrichous; amphitrichous. Structure/function of eubacteria E. Coli © Dennis Kunkel

21 21 Fimbria(e) Ultrastructure 7 Hair-like appendages not related to motility. Shorter and straighter than flagella Either polar or even distribution. Number from few to thousands. Enables adhesion. A factor in pathogenicity. Structure/function of eubacteria E. Coli © Dennis Kunkel

22 22 Pilus(i) Ultrastructure 8 Usually longer than fimbriae. Number only one or two. Join cells in preparation for transfer of DNA. Thus also known as sex pili. Structure/function of eubacteria

23 23 Structure/function of eubacteria Glycocalyx Ultrastructure 9 Layer of viscous material (usually polysaccharides) outside the cell wall. Observation: Indian ink stained specimens. When well defined: capsule. disorganized:slime layer. Function: Adhesion; protection against desiccation; prevent attachment by bacteriophages or attack by white blood cells.

24 24 Characteristics of viruses Living organisms? Inert outside a living host Obligatory intracellular parasites Either: complex aggregation of non-living chemicals or simple living microorganism. Distinctive features Single type of nucleic acid; DNA or RNA. Protein coat surrounds the nucleic acid (NA). Synthetic processes of a host living cell used to multiply. Specialized structures for transfer viral NA to other cells.

25 25 Characteristics of viruses

26 26 Viral structure Virion A complete, fully developed viral particle composed of nucleic acid surrounded by a protective coat which also serves as a vehicle of transmission from one host cell to another. Nucleic acid Contrasts with pro- and eucaryotic cells where DNA is the primary genetic material. Total NA: From a few thousand to as many as 250,000 nucleotide pairs. E. coli has 4 million nucleotide pairs. NA is single or double stranded; linear or circular. May be in separate segments e.g. influenza virus.

27 27 Viral structure Capsid Protein coat surrounding the nucleic acid. Capsomere: Protein subunits of the capsid. Arrangement is characteristic of each particular virus. Nucleocapsid: Capsid and nucleic acid as a unit. Capsids give virus types their typical shapes.

28 28 Viral structure Envelope Outer membranous layer; lipids, carbohydrates and proteins. Present in many animal and some plant viruses. In animal viruses: Host cell nuclear or plasma membranes contribute envelope lipids and carbohydrates. Envelope proteins are made by the virus. Some have spikes (a.k.a. peplomers); are carbohydrate-protein complexes. Thought to be involved in attachment to hosts. Useful in identification since they differ amongst viruses.

29 29 Viral structure Four general morphological types of virion structure Helical viruses Capsomeres arranged in a helical around the nucleic acid. Polyhedral viruses Capsids are icosahedral in arrangement (20 equilateral triangular faces and 12 corners). Enveloped viruses Roughly spherical but pleomorphic as the envelope is not rigid. Capsid can be helical or polyhedral. Non-enveloped viruses are naked viruses. Complex viruses Have capsid symmetry but neither purely helical or polyhedral.

30 30 Viral structure

31 31 The eucaryotic cell Protozoa, algae and fungi are eucaryotic.

32 32 The eucaryotic cell Ultrastructure Flagella and cilia Few and long - Flagella Short and few - cilia Motility; movement of substances (cilia) Both: 9 ring pairs and 2 central microtubules. Glycocalyx Surrounds animal cells. Strengthens cells; also means of attachment to other cell.

33 33 The eucaryotic cell Ultrastructure 2 Cell wall Algae and some fungi: cellulose. Fungi: chitin. Cytoplasmic membrane Like procaryotes: Phospholipid bilayer containing proteins. Contains CHO attached to proteins and sterols not found in procaryotes. Capable of endocytosis. Cytoplasm Resemble that of procaryotes. Has cytoskeleton and exhibits cytoplasmic streaming. Unlike procaryotes, many important enzymes are sequestered in organelles.

34 34 The eucaryotic cell Ultrastructure 3 Cell wall Algae and some fungi: cellulose. Fungi: chitin. Cytoplasmic membrane Like procaryotes: Phospholipid bilayer containing proteins. Contains CHO attached to proteins and sterols not found in procaryotes. Capable of endocytosis. Cytoplasm Resemble that of procaryotes. Has cytoskeleton and exhibits cytoplasmic streaming. Unlike procaryotes, many important enzymes are sequestered in organelles.

35 35 The eucaryotic cell Ultrastructure 4 Organelles Nucleus Contains DNA in the form of chromosomes. Most characteristic of eucaryotes.

36 36 The eucaryotic cell Ultrastructure 5 Organelles Endoplasmic reticulum Not present in procaryotes. Provides surface for chemical reactions. Serves as transport network. Stores synthesized molecules. Ribosomes Attached to outer surface of ER but also found free. Larger than procaryotic ribosomes. Site of protein synthesis.

37 37 The eucaryotic cell Ultrastructure 6 Organelles Golgi complex Consists of cisternae. Secretion; CHO and glycoprotein synthesis.

38 38 The eucaryotic cell Ultrastructure 7 Organelles Mitochondrion(a) Folding of inner membrane provides large surface area for chemical reactions e.g. ATP production (primary site) and cellular respiration. Can multiply on their own by fission.

39 39 The eucaryotic cell Ultrastructure 8 Organelles Lysosomes Formed from golgi complexes. Contain digestive enzymes to breakdown molecules and invasive bacteria. Centrioles Role in cell division and as basal bodies in the formation of flagella and cilia.

40 40 The eucaryotic cell Ultrastructure 6 Organelles Chloroplast Algae/green plants only. Contains DNA, ribosomes, chlorophyll and photosynthetic pigments. Can multiply on their own by fission.


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