Antibiotics Resistance Review

Antibiotics resistance ====================== **Conjugation**: Antibiotics resistance genes are on the plasmids and the plasmids can be transferred between bacteria via conjugation **Transformation:** sometimes genes are present in the environment and the bacteria can take it up from the environme...

Antibiotics resistance ====================== **Conjugation**: Antibiotics resistance genes are on the plasmids and the plasmids can be transferred between bacteria via conjugation **Transformation:** sometimes genes are present in the environment and the bacteria can take it up from the environment, this is called **Environmental Uptake** The third mechanism is transduction where its done by bacteriophages horizontal gene transfer in bacteria, and it involves **bacteriophages Infection**: A bacteriophage infects a bacterial cell by injecting its DNA into the host cell. **Transduction:**The bacteriophage\'s DNA takes over the bacterial cell\'s machinery, causing the bacteria to produce new phage particles. **Accidental Packaging**: Sometimes, bacterial DNA fragments are mistakenly packaged into new phage particles along with or instead of the phage DNA. **Transfer**: When these new phages infect another bacterial cell, they inject the bacterial DNA they carry, leading to the transfer of genetic material from the first bacterium to the second. Antimicrobial susceptibility typing: ------------------------------------ the two main methods for determining if bacteria are antibiotic resistant are: 1. Disk Diffusion (Kirby-Bauer Test): Antibiotic-impregnated disks are placed on an agar plate inoculated with bacteria. The effectiveness of the antibiotic is indicated by the size of the inhibition zone around the disk. certain sized zones of inhibition allows us to identify the type of bacteria and wither its antibiotic resistant or not 2. Broth Dilution (Minimum Inhibitory Concentration or MIC): This method involves exposing bacteria to different concentrations of an antibiotic in a liquid medium. The lowest concentration that prevents visible bacterial growth is the MIC, indicating the effectiveness of the antibiotic. History of microbiology ======================= Antonie van Leeuwenhoek ----------------------- **, made first microscope** A person in a robe and a person in a robe Louis Pasteur ------------- **Germ theory of fermentation** **Disproved spontaneous generation -- theory of abiogenesis.** **Organisms like maggots, mice, frogs and agents of food spoilage spontaneously generated from 'life force' present in inanimate materials.**  Robert Koch ----------- **Developed lab methods for growing microbes** **Founded laboratory microbiology: agar media, Petri plates, nutrient solutions, aseptic techniques, elucidation of bacterial species and staining techniques.** **Established link between SINGLE microbe & SPECIFIC disease (Koch's postulates).** Fermentation Pathways ===================== Some microbes, known as anaerobes, grow in the absence of oxygen through a process called fermentation. Fermentation is carried out by anaerobic bacteria and involves different pathways. For example, sugars are converted into lactic acid, acetic acid, and propionic acid. - **Lactic Acid**: Used in the dairy industry, particularly in the production of products like yogurt and cheese. - **Yeast (Saccharomyces cerevisiae)**: Plays a key role in baking and brewing by fermenting sugars to produce carbon dioxide and alcohol. A diagram of a food and wine Description automatically generated with medium confidence Pasteurisation ============== - **avoiding the spoilage of milk and wine and also to stop people getting sick from drinking these** - **Difference between pasteurisation and sterilisation** - **Is a proses where milk gets heated up to 70C and the cold down and then stored this proses reduces the number of bacteria, but it doesn't kill all of them** - **UHD milk has a longer shelf life because its sterilised.**  **KOCH\'S POSTULATES** 1. **The microbe must be present in every case of the disease (especially in \'lesions\').** 2. **The microbe must be isolated from an individual \'case\' and grown in axenic culture.** 3. **The disease must be reproduced when this pure culture is inoculated into healthy susceptible host.** 4. **The same microbe should be able to be re‐isolated from the infected host and grown in laboratory culture.** - **Presence**: Find the microbe in all cases of the disease. - **Isolation**: Grow the microbe in a pure culture from an infected individual. - **Reproduction**: Introduce the microbe to a healthy host and reproduce the disease. - **Re-isolation**: Isolate the same microbe from the newly infected host. **Characteristics of living things?** **Movement (bacteria are with their flagellum but not all bacteria are motile )** **Reproduction (they can also reproduce via conjugation, transduction and transformation)** **Sensitivity (like chemotaxis)** **Growth** **Respiration (bacteria can be anaerobic Aswell)** **Excretion** **Nutrition** Subdivision of cellular organism ================================  Prokaryotes =========== - **Genetic material (DNA) in cytoplasm** - **Bacteria are different from all eukaryotes (animals, plants, fungi, 'protists', etc.)** - **Includes organisms always regarded as bacteria --e.g. pathogens** - **Also includes photosynthetic bacteria** -- **e.g. the CYANOBACTERIA ('blue‐green algae')** Prokaryotic domains ------------------- - **Eubacteria (= Bacteria)** - **Archaebacteria (= Archaea)** - **key difference : membrane structure** - **usually biological membranes are phospholipid bilayer** - **contain fatty acids** - **Archaea have complex lipids, isoprene‐based can be linked together to form a monolayer** Bacteria and archaea membrane ----------------------------- Diagram of a hydrophobic structure Description automatically generated  Archaea membrane ================ A diagram of a structure Description automatically generated Classification based on Genetic information =========================================== When we isolate bacteria, we identify them based on morphological differences and biochemical characteristics. Before the advent of genetic methods, these were the primary techniques used to classify bacteria into different species. This approach was prevalent until the 1990s. In the 1990s, a new technique called multi-locus enzyme electrophoresis (MLEE) was introduced. MLEE analyzes the electrophoretic mobility of multiple enzymes encoded by different loci, providing a more precise method for distinguishing bacterial species and understanding their genetic relationships. A diagram of a dna sequence Description automatically generated Review: Features of bacteria ============================ - PROKARYOTES: no nucleus. - Organisation: *typically,* unicellular. - Diverse metabolism: - Heterotrophs/photoautotrophs - aerobes/anaerobes. - Cell Size: typically, \~1-2 mm. - Internal structure: no membrane-bound organelles. In Eukaryotic cells: organelles are often surrounded by a membrane similar in structure to the cell membrane but with a different composition of protein and phospholipid.  Classifying Bacteria ==================== **Description: prokaryotes, absorbers (what do they use as nutrients) , wet conditions(grow in water or not), animal decomposers, cell walls, unicellular** **Types: eubacteria, Archaebacteria, Gram‐negative, Gram‐positive, acid fast(they contain** mycolic acid **which makes the cell was more though allowing it to survive more environmental stress ), cyanobacteria** **Morphology: cocci, bacilli, spirals, etc.** **Nutrient Type: chemoheterotrophs, photoheterotrophs, chemoautotrophs, photoautotrophs** **Durable state: endospores (some)** **Diseases: tetanus, botulism, gonorrhea, Chlamydia, tuberculosis, etc., etc., etc. Ecological requirements: Oxygen, temperature, gender , since 1990s we sequenced 7 housekeeping genes allowed to understand evolution via multi locus enzyme electrophoresis , in 2005 on ward a new technique was developed called hole genome sequencing or next generation sequencing and by 2012 It become common to sequence the entire genome of bacterise** Energy Capturing Metabolism of Microorganisms: ============================================== Microorganisms are categorized based on their energy-capturing metabolism into two main groups: autotrophs and heterotrophs. 1. **Autotrophs**: - Autotrophs use inorganic compounds to convert them into organic compounds. There are two subtypes of autotrophs: - **Photoautotrophs**: These include green sulfur bacteria, purple sulfur bacteria, cyanobacteria, and algae. They use light as a source of energy. - **Chemoautotrophs**: These use inorganic compounds and do not necessarily rely on light energy for their metabolic processes. 2. **Heterotrophs**: - Heterotrophs rely on organic compounds for their energy needs. There are two subgroups of heterotrophs: - **Photoheterotrophs**: These organisms need organic compounds and generally use organic molecules for energy but sometimes can use sunlight as a supplementary source. - **Chemoheterotrophs**: These organisms exclusively use organic compounds for their energy requirements. A diagram of microorganisms Description automatically generated  Cell Shape (aka Morphology) - limited range - two most common: 1) Spherical Cells ------------------ - cocci (pl.), coccus (sing.) - may aggregate: - chains - 'streptococci' - clumps - 'staphylococci' - Pairs - diplococci *Neisseriae*  ### Spherical Cells: Division planes and cell arrangements A diagram of different types of cells Description automatically generated 2) Rods ============================= - bacilli (plural), **[bacillus]** (sing.) - from Latin - 'stick' - hence *Bacillus* genus e.g. *Bacillus anthracis* - But... many other rods exist \- so use **[ROD]** (not bacillus) Different types of cell division Description automatically generated  Structures of the bacterial cell ================================  Capsule or Mucilage layer ========================= - Also called Glycocalyx - Not essential for cell viability - Found in some bacteria - Outside cell wall - When well define -\> capsule - When less defined -\>Slime layer - Bactera that use capsule grow in small colonies - Usually, a single polysaccharide - Polysaccharide type can help identify species or strain - Functions of capsule/mucilage ============================= 1. ADHERENCE (capsule is sticky) - 'biofilms' 2. PROTECTION against water loss 3. PROTECTION against phagocytes (white cells) in pathogenic bacteria 4. PROTECTION against chemicals e.g. disinfectants 5. They help bacteria to adhere to different surfaces the pathogens form biofilm which helps to form capsules which are sticky the capules protect bacteria from water and macrophage Bacterial Cell Wall =================== - Structure: major component **[PEPTIDOGLYCAN or murein]** - Long (s)**[GLYCAN]** chains with repeating sub-units of: - \(i) N-acetylglucosamine(G) and - \(ii) N-acetylmuramic acids (M) - cross-linked by short **[PEPTIDE]** chains Underneath the capsule is the bacterial cell wall, which is essential for bacteria. The cell wall is primarily composed of a major component called peptidoglycan (or murein). The peptidoglycan is made up of two repeating units: N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM). The peptidoglycan monomers are synthesized in the cytosol of the bacterium where they attach to a membrane carrier molecule called bactoprenol. The bactoprenols transport the peptidoglycan monomers across the cytoplasmic membrane and work with other enzymes to insert the monomers into existing peptidoglycan enabling bacterial growth after the binary fission. The M and G subunits alternate and the peptide chains are connected by lysine interpeptide cross bridges  PEPTIDOGLYCAN ------------- - [UNIQUE] polymer (unique polysaccharide & peptide components) - forms a **single molecule** surrounding cell - very strong, yet permeable because they are need netruattds transported and secretion of proteins like toxins - target for anti-bacteria attack: - penicillin - lysozyme Two major types of cell wall ---------------------------- - due to major differences in cell wall structure (electron microscopy) - two groups termed.................. GRAM-POSITIVE and GRAM-NEGATIVE ### The bacterial envelope (wall + membranes) [Gram-positive bacteria] - relatively **[thick] cell wall** (\>20 nm) - **[high internal osmotic pressure]** (turgid) - **[high peptidoglycan]** content (\>50%) - wall contains **[other polymers (teichoic acids)]** - typically **[sensitive to lysozyme and penicillin]** - **[no further layers]** outside the cell wall Surface polymers such as teichoic acids play important roles in cell shape determination, regulation of cell division, pathogenesis and antibiotic resistance. Diagram of a gram positive envelope Description automatically generated ### The bacterial envelope (wall + membranes): [Gram-negative bacteria] - relatively [thin] cell wall (\