Bacterial_Morphology_2024 (1).pdf

Bacterial morphology and nomenclature Presented by Prof Vitali Sintchenko Faculty of Medicine and Health Originally developed by Dr Christina Adler Faculty of Medicine and Health The University of Sydney Page 1  Learning Objectives Know the terms to describe s...

Bacterial morphology and nomenclature Presented by Prof Vitali Sintchenko Faculty of Medicine and Health Originally developed by Dr Christina Adler Faculty of Medicine and Health The University of Sydney Page 1  Learning Objectives Know the terms to describe shapes & arrangements of bacteria Know the principles of Gram staining Know the difference between Gram-negative & Gram-positive bacteria Know the principles for naming organisms Understand the concept of a phylogenetic tree and how various species relate to each other in a tree The University of Sydney Page 2  Why focus on bacteria? Numerically most dominant cells in the oral cavity Important to oral health Causative agents in oral diseases The University of Sydney Page 3  Microbiomes consist of many different organisms https://draxe.com/health/oral-microbiome/ Gao et al. Protein Cell 2018;9(5):488 The University of Sydney Page 4 Morphology The University of Sydney Page 5  Bacterial shapes/morphology – Cocci (coccus, s.): round or spherical – Bacilli (bacillus, s.): rod-shaped – Spirochaetes (Spirilla): spiral-shaped – Other shapes: filamentous, curved, pleomorphic The University of Sydney Page 6  Bacterial arrangements – Clumps eg. Staphylococci – Chains eg. Streptococci – Twos/Diplo eg. Diplococci – Fours/Tetrads eg. Micrococci sp. – Eights/Cubic eg. Sarcina sp. The University of Sydney Page 7  Question Staphylococcus Streptococcus What bacterial shape is in the picture? A. Cocci B. Rod C. Spiral The University of Sydney Page 8  Question Gram-stain of coliforms What bacterial shape is in the picture? A. Cocci B. Rod C. Spiral Straight, short, evenly stained bacilli with parallel sides and rounded ends The University of Sydney Page 9  Question What bacterial shape is in the picture? A. Cocci B. Rod C. Spiral The University of Sydney Page 10  Bacterial colonies on solid media Bacteria grow on solid media as colonies. A colony is defined as a visible mass of microorganisms all originating from a single mother cell. Useful to identify type of bacterial species and characteristics: – colony form, elevation, margin – colony colour, size, texture – colony appearance The University of Sydney Page 11  Bacterial colony morphology Bacteria grow on solid media as colonies. A colony is defined as a visible mass of microorganisms all originating from a single mother cell. Useful to identify type of bacterial species and characteristics: – colony form, elevation, margin – colony colour, size, texture – colony appearance The University of Sydney Page 12  Bacterial cell properties D. A. B. C. The University of Sydney Page 13  Bacterial cell properties The University of Sydney Page 14  Review List the common features of bacterial cell structure Structure Function The University of Sydney Page 15 Gram staining The University of Sydney Page 16  Gram staining (after Christian Gram) – Most widely used staining method in bacteriology – Gram positive bacteria = purple – Gram negative bacteria = pink/red Gram-Positive Gram-Negative (e.g.Staphylococcus aureus) (e.g. Escherichia coli) The University of Sydney Page 17  Gram positive and negative bacteria Type of Cell wall Example bacteria properties Gram Thick cell wall Streptococcus positive oralis More peptidoglycan 20-80 nm Gram 2 x thin cell Escherichia negative walls coli Less peptidoglycan 2-7 nm The University of Sydney Page 18  Gram positive and negative bacteria in oral cavity The University of Sydney Page 19  Streptococcus – Gram positive – Cocci shaped – Major genus in the mouth, both in health & disease – Some can lyse red blood cells to various degrees – Health-related: S. gordonii, S. salivarius, S. sanguis – Disease-related: S. pyogenes, S. mutans The University of Sydney Page 20  Bacteroidetes – Gram negative – Rod shaped – Major genus in the mouth, both in health & disease Tannerella forsythia – Disease-related: Tannerella Tannerella forsythia forsythia, Porphyromonas gingivalis – Q. Which type of bacteria (Gram +ve or –ve) is “hardier”? The University of Sydney Page 21  Not all bacteria have a cell wall Some bacteria have no cell wall = no staining Potential of alternative classification system for bacteria Long history of gram stain system The University of Sydney Page 22 Nomenclature The University of Sydney Page 23  Classification of bacteria Historical criteria Staining (Gram-positive or Gram-negative) Shape (rods, cocci) Respiration (i.e. aerobes = require O2, anaerobes = require CO2) Reproduction [clusters = staphylococci; chains = streptococci; pairs = diplococci] Modern criteria Genomic similarity (DNA sequence similarity to reference sequences) The University of Sydney Page 24  Classification of bacteria The University of Sydney Page 25  Naming convention: Linnaeus convention Latin name Genus species strain Escherichia coli K1 Strain: the descendants of a single cell with a distinct characteristic(s). Species: In prokaryotes: a collection of strains that share many stable properties and differ significant from other groups of strains. Genus: group of species exhibiting similar characteristics The University of Sydney Page 26  Naming convention Means ‘abnormal, produced by mutation’ Streptococcus species Streptococcus mutans Streptococcus oralis Genus name capitalised species name lower case Written in italics The University of Sydney Page 27  Similarity between bacterial genomes The University of Sydney Page 28  Relationships of species to each other The University of Sydney Page 29  Phylogenetic tree – Based on genetic data – Tips represent nucleotide sequences – Origin = last common ancestor – Branching points represent a divergence event – More distance between tips reflects greater number of genetic changes The University of Sydney Page 30  Oral bacteria tree The University of Sydney Page 31  Questions 1. Why are viruses not on the “tree of life” A. They are cellular B. They are not considered living C. They contain membrane bound organelles 2. What feature of gram-positive bacteria causes them to stain purple with a gram stain? A. Thin cell wall B. Thick cell wall C. Thick cell capsule D. Thick plasma membrane The University of Sydney Page 32  Summary – Common bacterial shapes include cocci, rods and spirals, in addition to less common shapes. – Bacteria can be arranged together or larger colonies – A major division between bacteria is based on cell wall structure and the staining of this = gram stain – Gram positive bacteria have a thick cell wall – Gram negative bacteria have a thin cell wall – Both are common in the oral environment – Naming is based on the Linnaeus convention – Relationships between bacteria are often represented by a phylogenetic tree The University of Sydney Page 33  COMMONWEALTH OF AUSTRALIA Copyright Regulation WARNING This material has been reproduced and communicated to you by or on behalf of the University of Sydney pursuant to Part VB of the Copyright Act 1968 (the Act). The material in this communication may be subject to copyright under the Act. Any further reproduction or communication of this material by you may be the subject of copyright protection under the Act. The University of Sydney Page 34