Classification of Microorganisms PDF

CLASSIFICATION OF MICROORGANISMS Dr. Anna Kafintu-Kwashie (MLS.D, Mphil ) SBAHS, korle -bu Classifications of micro organisms Organisms are generally organized into subspecies, species, genera, families, and higher orders. Classification of bacteria is t...

CLASSIFICATION OF MICROORGANISMS Dr. Anna Kafintu-Kwashie (MLS.D, Mphil ) SBAHS, korle -bu Classifications of micro organisms Organisms are generally organized into subspecies, species, genera, families, and higher orders. Classification of bacteria is the orderly arrangement of bacteria in groups Classification of Microorganisms  Cells are divided into two basic types, which are as follows: 1. Prokaryotic cells 2. Eukaryotic cell  Prokaryotic cells are smaller when compared with eukaryotic cells. In Prokaryotic , the cytoplasm is enclosed by the cell membrane, the cell organelles freely float, without any membrane, in this cytoplasm. Nucleus is called nucleoid as it lacks the membrane surrounding it; that is, it contains a naked DNA molecule. Blue green algae and bacteria are examples of prokaryotes. Prokaryote and Eukaroyte Eukaryotic are organisms that can be multicellular or unicellular cell organism Examples are protists, plants, fungi or animals. Similarites between prokaryotic and Eukaroytic ( both have DNA, Ribosomes, cytoplasm, cell membrane, Most have cell wall but not animal cells Differences between Prokaryotic and Eukayotic cell Prokaryotic cells Eukaryotic cell They lack a true nucleus to contain DNA They have a well defined nucleus and have a nucleoid region where the genetic material is found in a form of a circular DNA molecule No membrane bound Organelles Have Membrane bound organelles (nucleus , mitochondria, Endoplasmic reticulum, Golgi apparatus Depending on the type of Eukaryotic, plant cells have chloroplasts whilst Animal cell do not have Size - They are usually smaller in size with a They are usually larger with a size range size range from 0.5 to 5um from 10 to 100um Cell division (divide by Binary fission) Cell division (divide by mitosis for somatic cells and meiosis for reproductive cells) Differences between Prokaryotic and Eukayotic cell Prokaryotic cells Eukaryotic cell Cell wall – many have cell walls which Plants cells have cell walls, composed of provide structural support, shape and cellulose, while animal cells lacks cell wall protection Flagella and Cilia – are used for Have both flagella and cilia and more locomotion and ar structurally different compex internal structures Reproduction- reproduce rapidly by binary Reproduction is generally slow due to the fission complexity of mitosis ad meiosis Genetic Material- They have a single Genetic Material – they have multiple circular DNA molecule linear molecules organized into chromosomes  BACTERIA CELL Bacteria are single-celled microorganisms with prokaryotic cells, which are single cells that do not have organelles or a true nucleus and are less complex than eukaryotic cells. COMMON FEATURES NUCLEUS CYTOPLASM CELL WALL THE BACTERIAL CELL  Characteristics of bacteria Bacteria are single-celled organisms. They lack organelles such as chloroplasts and mitochondria, Do not have the true nucleus. Their DNA, a double strand that is continuous and circular, located in a nucleoid. Have a cell membrane and a cell wall that is often made of peptidoglycan. Reproduction occurs through binary fission Bacterial morphology and arrangement Bacteria have one of three a. Rod (bacilus) basic shapes, b. Cocci (coccus) spherical Coccus (round or oval) c. Curve Spiral (curve, spiral, or d. Pairs twisted) e. Rods in chains Bacillus (rod-shaped) f. Cocci in chains g. Cocci in Tetrads h. Cocci in clusters  Cocci: These are round or oval bacteria measuring about 0.5 – 1.0 µm in diameter. When multiplying cocci may form i. Pairs: called diplococci eg, meningococci and gonococci. ii. Chains: called streptococci eg, streptococcus pyogenes. iii. Groups: called staphylococci eg, Staphylococcus aureus  Bacilli These are stick-like bacteria with rounded, tapered (fusiform), square or swollen ends. Short rods with rounded ends are often called cocciobacilli. They may Form chains eg Streptobacilli species. Form branching chains eg, lactobacilli. Mass together eg, Mycobacterium leprae. Attached at various angles resembling Chinese letters eg Corynebacterium diphtheria  Vibrio These are small slightly curved rods measuring 3 – 4µm in length by 0.5µm in width. Vibrios are comma-shaped rods with a small twist. Most vibrios are motile with single flagellum at one end. They show a rapid darting motility eg, Vibrio cholera.  Spiral Bacteria Spiral bacteria are twisted and commonly occur in two forms: Spirillum (spirilla plural) Spirochetes. These cells resemble long, twisted coils.  Spirilla bacteria Spirilla bacteria are elongated, spiral-shaped, rigid cells. These cells may also have flagella, which are long protrusion used for movement, at each end of the cell. An example of a spirillum bacterium is Spirillum minus, which causes rat-bite fever.  Spirochetes Spirochetes bacteria are long, tightly coiled, spiral-shaped cells. mmThey are more flexible than spirilla bacteria. Examples of spirochetes bacteria include 1. Borrelia burgdorferi, which causes Lyme disease 2. Treponema pallidum, which causes syphilis. Spirochaetes are divided into three groups  Treponemes eg: Treponema pallidum, Treponema pertenue.  Borreliae eg: Borrelia duttoni, Borrelia vincenti.  Leptospires eg: Leptospira interrogans,  Ricketsiae Although classified as bacteria ricketsiae resemble viruses in that they replicate only in living cells and are unable to survive as free-living organisms. Unlike viruses the ricketsiae contain both DNA and RNA, multiply by binary fission and have cell walls composed of peptidoglycan.  NUCLEUS BACTERIA ANIMAL Prokaryotic=primitive Eukaryotic=true nuclear structure nucleus No nuclear membrane Nuclear membrane One chromosome Many chromosomes  NUCLEUS Also called-nucleoid, nuclear body Genetic information 1mm long, double stranded DNA, circular Coiled up (like wool) Stains with Giemsa but not the usual bacterial stains Usually only one per cell  CYTOPLASM BACTERIA ANIMAL Nuclear organelles No internal membranous Mitochondria structures Golgi apparatus Endoplasmic reticulum RIGID CELL WALL  Cytoplasm Watery soft gel Cytoplasmic inclusions- Granules – store of reserve material lipid, polysaccharide, volutin Contains-organic & inorganic solutes Vitamins Coenzymes Ribosomes Network of fine fibrils with connections extending to the nucleus  Cytoplasmic membrane An important feature of all bacteria Visible by Microscopy Typical unit membrane 10% of dry weight of the cell Delicate membrane, described as a fluid mosaic  Functions of cytoplasmic membranes 1. Selective permeability-active, passive 2. Electron transport-like mitochondria 3. Excretion of hydrolytic enzymes 4. Has receptors for chemotactic system 5. Has enzymes and carrier molecules for synthesis of DNA and cell wall  Bacteria cell Wall The cell wall is mainly made up of murein (also called peptidoglycan), which is a polysaccharide chain cross-linked by peptides containing d- amino acids. Bacterial cell wall is made up of peptidoglycan, fungi cell wall of chitin, and plant cell wall of cellulose. Archaea differ from bacteria by lacking peptidoglycan in their cell wall. In bacteria, two different types of cell wall composition can be seen, one in Gram positive bacteria and the other in Gram-negative bacteria NB: bacteria are classified as gram positive or gram negative according to their response to the Gram staining procedure.  CELL WALL Rigid, 10-25 nm thick Supports the weak cytoplasmic membrane Gives bacteria it’s shape Can withstand the high osmotic pressure in the cell (5- 25 atmospheres) Mycoplasma has no cell wall Cell Wall Differences between Gram-Positive and Gram-Negative Bacteria GRAM +VE GRAM -VE Mainly peptidoglycan Little peptidoglycan, between two unit Lipoteichoic acids membranes Potential space is- Teichoic acids periplasmic space Lipoprotein attached to outer membrane Lipopolysaccharides LPS GRAM +VE BACTERIA Mainly peptidoglycan Lipoteichoic acids Teichoic acids GRAM –VE BACTERIA Little peptidoglycan, between two unit membranes Potential space is- periplasmic space Lipoprotein attached to outer membrane Lipopolysaccharides LPS EXTERNAL STUCTURES FLAGELLA Flagellin PILI (fimbria) Pilin CAPSULE Protein Polysaccharide Polypeptide ARRANGEMENT OF FLAGELLA  STRUCTURES INVOLVED IN ATTACHMENT 2. Glycocalyx - forms multicellular aggregates by binding the cells together. Some bacteria are involved in plaque formation leading to dental caries. 3. Pili: similar to fimbriae but are fewer (sometimes only one per cell) and longer. F-pilus (sex pilus) fertility factor. (a) Pili that act as receptor sites for attachment of some phages (b) Pili that act as sex pili for bacterial conjugation processes/ Adhesion to mucosal surfaces during colonization (c) Pili that help in the attachment of pathogenic bacteria to human tissues  External structures 1. Flagella: Flagella are whip-like structures protruding from the bacterial cell wall and are responsible for bacterial motility (i.e. movement). Organisms which are motile are vibrios, spirilla and spirochetes. The fagellum is made up of thousand molecules of a protein subunit called Flagelin. The arrangement of flagella include: Peritrichous - Multiple flagella found at several locations about the cell Polar - Single flagellum found at one of the cell poles. (Monotrichous) Lophotrichous - A tuft of flagella found at one cell pole  Capsule Capsule function Firm gelatinous material- Protects against damage and wide/microcapsule destruction Antigenic, different strains such as Lysozyme, differ Phagocytosis, etc Addition of anticapsular AB causes increase in size Seen by negative staining  Bacteria Identification There are several other approaches also to classify bacteria based on different aspects, which are discussed in the following sections. Some bacteria can be identified through simple visual inspection. Identification first begins with evaluating the appearance of the bacterial colony followed by examination under the microscope for considering their shape, groupings, and features such as the number and location of flagella. Staining techniques are employed to mediate identification in addition to various culture techniques such as the use of differential special culture medium. Many other biochemical tests are employed to identify bacterial by- products, and sophisticated tests (Polymerase Chain Reaction based) are available to analyse the DNA of the bacteria  Bacteria Identification (Morphological identification) Based on their morphology, the bacteria can be divided into the following groups: 1. Filamentous or higher bacteria (actinomycetes) 2. (a) Gram-positive bacilli (i) Aerobes (e.g., Corynebacterium and Bacillus) (ii) Anaerobes (e.g., Clostridium and Lactobacillus) (b) Gram-positive cocci (c) Gram-negative cocci (d) Gram-negative bacilli  NUTRITIONAL CLASSIFICATION Based on their energy requirements, the bacteria can be classified into the following: 1. Energy classification (a) Phototrophs: They derive energy from sunlight. b) Chemotrophs: They use chemicals to derive energy. 2. Based on their ability to synthesize essential metabolites, the bacteria can be classified into the following: (a) Autotrophs: They synthesize organic compounds from carbon dioxide and nitrogen. (b) Heterotrophs: They depend on preformed organic compounds (e.g., pathogens). 3. Based on their oxygen requirements, the bacteria can be classified into the following: (a) Aerobes (b) Anaerobe  Bacteria Identification NUTRITIONAL CLASSIFICATION- 4. Based on temperature, the bacteria can be classified into the following: (a) Psychrophiles (below 20°C) (b) Mesophiles: (25°C to 40°C) (c) Thermophiles: (55°C to 80°C)  BIOCHEMICAL CLASSIFICATION 1. Lactose fermenting 2. Non-lactose fermenting 3. Late lactose fermenting 4. Production of indole, H2 S, catalase, oxidase, urease etc CLASSIFICATION BASED ON STAINING REACTION 1. Based on Gram staining, the bacteria can be classified into the following: (a) Gram-positive bacteria (b) Gram-negative bacteria 2. Based on acid-fast staining, the bacteria can be classified into the following: (a) Acid-fast bacilli (b) Non-acid-fast bacill  Staining techniques by Grams Method Make slide by smear, drop, or cytocentrifuged samples Gram stain Crystal violet: primary stain Gram’s iodine: mordant/fixative Acetone-ethanol: decolorizer Safranin: counterstain 42 Gm+ve cocci & Gm-ve bacilli 43  Staining techniques for Mycobacterial species (Acid-fast stains) – for staining of organisms with high degree of fatty (mycolic) acids— waxy render the cells resistant to decolorization: “acid-fast” Mycobacterium sp., Nocardia sp., Cryptosporidium sp. are acid-fast Procedure Ziehl-Neelsen heat drives in primary stain (carbolfuchsin) Decolorize with 20% sulpheric acid (H2SO4) Counterstain with methylene blue or malachite green 44 Mycobacteria species 45