Microbes: Viruses, Bacteria, Protista, and Fungi

• Microbes (micro-organisms) are organisms too small to be visible without a microscope
• Four main groups of microbes: viruses, bacteria, protista, and fungi
• Microbes are everywhere and usually coexist peacefully
• Some microbes, like gut bacteria, aid in digestion
• Pathogens are microbes that can cause illness

Microbe Groups

• Viruses: e.g., HIV

• Bacteria: e.g., TB

• Protista: e.g., Plasmodium (causes malaria)

• Fungi: e.g., Candida

• Micro-organisms are used in: alternative fuel production (methane), enzyme and pharmaceutical production, sewage treatment and biodegradation

• Some micro-organisms are parasites and pathogens that cause diseases

• Diseases caused by microbes include:

• Viral: HIV/AIDS, influenza, measles, herpes

• Bacterial: sore throat, gangrene, tuberculosis, cholera, syphilis

• Protist: malaria, sleeping sickness, dysentery

• Fungal (mycoses): ringworm, athlete's foot, candidiasis

• Pathogens cause sneezing, coughing, and fever to spread disease

• Some microbes spoil food or produce toxins

• Microbes compete with humans for food nutrients

• Rapid growth gives microbes the advantage

• Microbial growth makes food unfit for consumption

• Micro-organisms used to make products

• They play roles in medicine and are used in biotechnology and genetic laboratories

• Some bacterial species clean up oil spills

Micro-organisms as Food

• Mushrooms (fungi) are edible
• Red and brown algae (protists) are consumed
• Brown alga Laminaria used in Asian soups
• Red alga Porphyra used to wrap sushi

Micro-organisms in the Food Industry

• Bacteria and fungi used in the fermentation of yogurt, cheese, beer, and wine
• Other products include vitamins and algin from red algae cell walls

Micro-organisms in Manufacturing

• Used to produce adhesives, paints, and cosmetics

Viruses

• Viruses are non-living and not technically classified into a kingdom
• Viruses require a host cell to replicate
• Virus structure: protein coat/capsid, nucleic acid core (DNA or RNA)
• Some viruses: spikes for attachment or a lipid envelope for protection

Viral Replication

• Viruses need a host to replicate
• Virus replication involves creating thousands of copies inside a host cell, which then leave to find other hosts
• Viruses cause disease by damaging or destroying cells as they leave
• All viruses are pathogenic, causing disease

Influenza (Flu)

• Can be transmitted directly or indirectly
• Direct transmission: infected person passes the virus directly to an uninfected person
• Indirect transmission: uninfected person touches a contaminated surface and then infects themselves

Symptoms of influenza:

• Central: headache.
• Systemic: fever (usually high).
• Muscular: extreme tiredness.
• Nasopharynx: runny or stuffy nose, sore throat, aches.
• Respiratory: coughing.
• Joints: aches.
• Gastric: vomiting.

HIV

• HIV (human immunodeficiency virus) attacks T-lymphocytes/CD4 cells, which are important for immune defense
• Two types of lymphocytes:
• B-lymphocytes: produce antibodies to neutralize foreign organisms
• T-lymphocytes: help B-lymphocytes identify foreign invaders
• HIV reduces CD4 cell count, decreasing immunity
• Leads to opportunistic infections like pneumonia or TB, progressing to AIDS (Acquired Immunodeficiency Syndrome)
• HIV has few initial symptoms, enabling its spread
• ARVs (anti-retroviral medications) prolong life and alleviate symptoms, but no cure or prevention exists

Basic Facts of HIV/AIDS:

• Transmission modes: sexual intercourse, blood/blood products, shared needles/syringes, from infected mother to child
• Prevention methods: abstinence, faithfulness, condoms, not sharing needles
• HIV/AIDS is NOT transmitted through: toilets, sharing utensils, mosquitoes

Bacteria

• Bacterial cells are surrounded by a rigid, protective cell wall
• Cell membrane regulates the passage of materials
• DNA genetic information is in the nucleoid
• Ribosomes carry out protein synthesis
• Pili extend out of the cell to transfer DNA
• Flagellum is used for locomotion
• Plasmid - small circular chromosome with extra genes
• Capsule - slimy substance that protects from white blood cells

Division

• Bacteria divide to form two identical daughter cells
• Happens as often as every six minutes
• Binary fission is bacterial cell division

Tuberculosis (TB)

• Caused by Mycobacterium tuberculosis bacteria, mainly affecting the lungs

• Tuberculosis is curable and preventable

• Transmitted through the air

• Only a few bacteria need to be inhaled to become infected

• One-third of the world's population has latent TB, meaning they are infected but not ill and cannot transmit the disease

• People with compromised immune systems (HIV, malnutrition, diabetes, tobacco users) have a higher risk of developing TB

• Active TB symptoms may be mild for months

• Those who are ill with TB can infect 10-15 other people in a year

• Without treatment, two-thirds of people ill with TB die

Drug-Resistant TB

• MDR-TB: Strain that thwarts the two most powerful of first line drugs
• Drug resistance is caused by: Incorrect prescription, erratic supply of drugs, poor quality drugs and Patient non-adherence