Aerobic Bacteria and Their Specific Culture Media - Microbiology PPT by Nikhitha.pptx

This PowerPoint presentation explains the characteristics of aerobic bacteria, with examples like Pseudomonas, Mycobacterium, and Bacillus. It also covers specific culture media like Nutrient Agar, MacConkey Agar, and Blood Agar, used for isolating and growing aerobic bacteria in microbiology labs.

1. Aerobic bacteria and Specific Culture Medium Submitted by G. Nikhitha P242025 M.Sc. Microbiology Central University of Tamilnadu

2. Overview : Introduction Types of Aerobic Bacteria Importance of Aerobic Bacteria Pathogenic aerobic bacteria Genes in aerobic bacteria Culture medium for Aerobic bacteria and its types Culturing of aerobic bacteria procedure Conclusion

3. INTRODUCTION : Bacteria that survives and grows only in presence of oxygen in their environment i.e., 21% Oxygen and 0.03% Carbon dioxide They need Molecular oxygen for survival and growth .Use oxygen as the final electron acceptor-respiratory chain. Aerobic respiration in bacteria used to derive energy from Oxidative phosphorylation and krebs cycle (also called as TCA cycle / Citric acid cycle ) and some part of the energy from Glycolysis Such bacteria possess Catalase, Peroxidase, and Superoxide dismutase enzyme to neutralize the Reactive oxygen species (ROS) generated due to aerobic respiration. Examples: Lactobacillus, Nocardia , Mycobacterium tuberculosis , etc.

4. Environmental Distribution: Ubiquitous in nature and can be found in diverse habitats. They play crucial roles in soil fertility, decomposition of organic matter, nitrogen cycling. ecological balance in ecosystems. In aquatic environments, aerobic bacteria contribute to water purification by degrading organic pollutants. Medical Significance : While many aerobic bacteria are harmless or beneficial, some species can cause infections in humans and animals. Ex: E.coli, S. Aureus, P.aeruginosa, and Mycobacterium tuberculosis.

5. Types of Aerobic Bacterium Aerobic Bacteria can be classified as: Obligate Aerobes : organisms that cannot survive in the absence of oxygen. The enzymes involved in the respiratory chain in obligate aerobes are catalase, peroxidase, and superoxide dismutase. Ex. Bacillus, Mycobacterium, and Pseudomonas. Facultative Aerobes : They can survive even in the absence of oxygen, do not entirely rely on the availability of oxygen in their environment. these bacteria utilize anaerobic methods to produce ATP/energy molecules.Ex, Enterobacteriaceae . Microaerophiles: Need only a small amount of oxygen for the generation of energy. The presence of oxygen in higher amounts can be lethal to microaerophiles. lack an electron transport system and are dependent on the fermentation reaction to generate energy.Ex: Helicobacter and Campylobacter. Aerotolerant Aerobes : do not utilize oxygen for a metabolic activity or for the generation of energy. They are also not adversely affected by the presence of oxygen. Aerotolerant bacteria do not possess enzymes (particularly, catalase , peroxidase , and superoxide dismutase) required for aerobic respiration.Ex: Lactobacilli and Streptococci.

6. Importance of Aerobic Bacteria: Decomposition and Nutrient Recycling. They break down complex organic compounds into simpler forms, releasing nutrients. This process is vital for nutrient recycling and maintaining soil fertility. Water and Soil Quality: purifies water and soil by degrading pollutants and contaminants. Bioremediation: To clean up polluted environments. Food Production: Aerobic bacteria are used in fermentation processes to produce yogurt, cheese, vinegar, and fermented vegetables . These bacteria contribute to flavor development, preservation, and food safety. Biotechnology: Aerobic bacteria used in the production of enzymes, antibiotics, vitamins , and other bioactive compounds through fermentation processes. Environmental Balance: Ecological balance in natural ecosystems. Research and Education: Aerobic bacteria are extensively studied in microbiology and biotechnology research. They serve as model organisms for understanding cellular processes, metabolic pathways, antibiotic resistance mechanisms, and microbial interactions, contributing to scientific knowledge and education.

7. Pathogenic aerobic bacteria Escherichia coli (E. coli) is a common bacterium that can cause foodborne illnesses, including diarrhoea, abdominal pain, and severe complications like haemolytic uremic syndrome (HUS). Staphylococcus aureus is a common cause of skin infections, pneumonia, sepsis, and toxic shock syndrome (TSS), with toxins contributing to its pathogenicity. Pseudomonas aeruginosa is often associated with hospital-acquired infections, particularly in immunocompromised individuals or those with cystic fibrosis. Mycobacterium tuberculosis (TB) is a major global health concern, causing symptoms like coughing, chest pain, weight loss, and fatigue. Legionnaires' disease , a severe form of pneumonia, is caused by Legionella pneumophila, which thrives in water systems. Haemophilus influenzae , despite its name, is not the cause of influenza but can cause respiratory tract infections like pneumonia and bronchitis. Salmonella s pp ., including Salmonella enterica, can cause salmonellosis, a common foodborne illness with symptoms like diarrhoea, fever, abdominal cramps, and vomiting. These pathogenic aerobic bacteria can be found in contaminated food, water, and animal products.

8. Genes seen in Aerobic Bacteria Respiratory genes include cytochrome c oxidase , cytochrome bd oxidase , NADH dehydrogenase , and ATP synthase . Metabolic genes include glycolysis , the Krebs cycle , and oxidative phosphorylation . Oxygen sensing and response genes enable aerobic bacteria to sense oxygen levels and respond accordingly. Antioxidant defence genes, such as catalase, superoxide dismutase, and peroxidases, help detoxify reactive oxygen species (ROS) and protect cellular components from oxidative damage. Transporter genes, such as ATP-binding cassette (ABC) transporters, ion channels, and permeases, facilitate nutrient uptake and waste elimination. Regulatory genes control gene expression in response to environmental cues, nutrient availability, and metabolic demands. Virulence genes, found in pathogenic species, contribute to the bacteria's ability to cause infections by encoding toxins, adhesion proteins, secretion systems, and other virulence factors.

9. Culture medium for Aerobic Bacteria: A suitable culture medium for an aerobic bacterium should support its growth while providing oxygen. The choice depends on the bacterial species, but common culture media include: General-Purpose Media (for many aerobic bacteria) Nutrient Agar (NA) – Basic medium for non-fastidious aerobic bacteria. Luria-Bertani (LB) Agar/Broth – Used for culturing bacteria like E. coli . Tryptic Soy Agar (TSA) or Broth (TSB) – Supports a wide range of aerobic bacteria. Enriched Media (for Fastidious Aerobic Bacteria) Blood Agar – Used for aerobes like Streptococcus , Staphylococcus . Chocolate Agar – Supports aerobic Neisseria and Haemophilus species. Brain Heart Infusion (BHI) Agar/Broth – Good for aerobic and facultative anaerobes. Selective & Differential (Can Support Aerobic Bacteria, But Not Exclusively) MacConkey Agar – Primarily for Gram-negative facultative aerobes. Mannitol Salt Agar (MSA) – Selective for Staphylococcus species, which are aerobes.

10. Culturing of Aerobic bacteria 1.Prepare Culture Media: Select an appropriate culture medium based on the requirements of the bacteria being cultured (e.g., Nutrient agar, Tryptic soy agar). Follow the manufacturer's instructions to prepare the culture medium, which typically involves adding the appropriate amount of agar to a liquid medium, sterilizing the mixture, and pouring it into petri dishes to solidify. 2. Sterilize Equipment and Work Area: Autoclave or sterilize all equipment and materials that will come into contact with the culture medium, such as petri dishes, pipettes, inoculating loops, and culture tubes. Clean and disinfect the work area, including the laboratory bench and any surfaces where cultures will be handled. 3 . Inoculation: Use a sterile inoculating loop or swab to transfer a sample of the bacteria to be cultured onto the surface of the solidified agar medium in a petri dish. This can be done by streaking the sample in a pattern (e.g., Quadrant streaking ) to obtain isolated colonies. 4 . Incubation: Seal the petri dish with parafilm or tape to prevent contamination and place it upside down (agar side up) in an incubator set to the appropriate temperature and oxygen level for the cultured bacteria (usually around 37°C for human-associated bacteria). Incubate the cultures for a specific period (usually 24 to 48 hours) to allow the bacteria to grow and form visible colonies on the agar surface. 5. Observation and Identification: After incubation, observe the petri dishes for bacterial growth. Aerobic bacteria typically form colonies that are smooth, round, and raised, with distinct characteristics depending on the species. Use appropriate techniques for bacterial identification, such as Gram staining, biochemical tests (e.g., Catalase test, Oxidase test), and molecular methods (e.g., PCR, Sequencing) to identify the cultured bacteria to the genus and species level.

11. 6.Subculture and Maintenance: If further testing or storage is required, subculture isolated colonies onto fresh agar plates or into culture tubes containing liquid medium for preservation. Store bacterial cultures in a suitable environment (e.g., Refrigerator for short-term storage, -80°C Freezer or Liquid nitrogen for Long-term storage) to maintain viability and purity. 7.Sterilize and Dispose: Properly dispose of used culture materials and contaminated items by Autoclaving or following laboratory safety protocols for disposal of biohazardous waste. Preparation of culture medium All materials required Sterilization (Autoclave) Inoculation Incubation Observation and Identification De-Contamination Disposal

12. Conclusion REFERENCES Madigan, M. T., Bender, K. S., Buckley, D. H., Sattley, W. M. (2018). Brock Biology of Microorganisms. Pearson. Prescott, L. M., Harley, J. P., Klein, D. A. (2019). Microbiology. McGraw-Hill Education. Tortora, G. J., Funke, B. R., Case, C. L. (2017). Microbiology: An Introduction. Pearson. Pelzer, M. J., Chan, E. C. S., Krieg, N. R. (2018). Microbiology: Concepts and Applications. McGraw-Hill Education. Aerobic bacteria play a crucial role in various biological and industrial processes, requiring specific culture media for optimal growth and identification. Selecting the appropriate medium ensures accurate isolation, characterization, and study of these bacteria in clinical, environmental, and research applications. Understanding their metabolic and oxygen requirements is crucial for improving microbial studies and applications.