Microbiology: Unveiling the Microscopic World and its Impact

Microbiology: The Science of Microorganisms

Microbiology, derived from the Greek words mikros ("small"), bios ("life"), and logos ("study"), is the scientific discipline dedicated to the study of microorganisms. These are living things too small to be seen with the naked eye. Microorganisms, often called germs, were discovered over 300 years ago. Their only common characteristic is their small size.

Microscopy depends on factors such as contrast, resolution, and magnification.

Taxonomy involves the study of nomenclature, classification, and identification of microorganisms.

Factors Influencing Microbial Growth

The number and types of microorganisms in an environment depend on factors like humidity, heat, nutrient availability, aeration, and pH.

• Soil Fertility: Fertile soil is rich in humus, an organic material composed of microbes.
• Fungi: Fungi in the soil break down cellulose, lignin, and pectin.
• Algae: Algae prevent soil erosion and contribute oxygen through photosynthesis.
• Microbial Activity: Increased microbial activity raises humidity and temperature. pH and oxygen availability are also crucial.
• Protozoa: Protozoa control bacterial populations by ingesting bacteria.
• Fungi: Help retain water and are responsible for the smell of damp earth.
• Mineralization: Soil microorganisms act as biogeochemical agents, converting complex organic compounds into simple inorganic ones.
• Bacteria: Bacteria are the most populous microorganisms in soil, including autotrophic, heterotrophic, aerobic, and anaerobic types.

Microscopy and Key Figures

Transmission electron microscopy (TEM) offers higher resolution than optical microscopy, using an electron beam to visualize objects.

• Koch: Studied anthrax, a disease affecting cows, sheep, and humans.
• Francesco Redi: Demonstrated that spontaneous generation of microscopic animals does not occur.
• Robert Hooke: Contributed to the first cell theory.

Types of Fungi

• Zygomycetes: Molds
• Ascomycetes: Morels
• Basidiomycetes: Mushrooms

Saprophytic fungi feed on waste from other living organisms, such as rotting corpses, dead skin, and dead leaves. Fungi are found in aquatic and terrestrial environments and can grow in acidic substances.

Protozoa and Their Characteristics

Protozoa move using specialized cellular structures called cilia.

Holozoic protozoa feed on other organisms, such as bacteria, yeasts, algae, and other protozoa.

Cytoproct: A defined region in some protozoa for eliminating indigestible waste.

Microorganisms have wide applications in industry, such as fermentation (for producing alcoholic beverages or dairy products) and the production of antibiotics, hormones, and enzymes.

Unique Microbial Groups

• Imperfect fungi: Reproduce exclusively through conidia, not ascospores or basidiospores.
• Phylum Oomycetes: Reproduce by spores and zoospores with flagella.
• Mycoplasma and bacteria: Seem to be intracellular parasites controlled with antibiotics. They grow and reproduce within a living cell and do not form spores.

Specific Mycoplasma Species

• Mycoplasma hominis: A pathogen found in the cervix of asymptomatic women.
• Mycoplasma genitalium: Isolated mainly from the genitourinary tract but can also be found in the respiratory tract.

Rickettsia and Related Bacteria

• Rickettsia-like bacteria: Reproduce by fission, grow and reproduce inside living cells, and are unicellular.
• Rickettsia characteristics: Non-motile, do not form spores, survive only within a cell, and are found in parasites that feed on blood.
• Erythrocytes: Anaplasma (family Anaplasmaceae) causes anaplasmosis, leading to anemia by destroying red blood cells.

Mycoplasmas have the smallest genomes among bacteria, meaning they do not synthesize amino acids, fatty acids, and vitamins.

Diseases Caused by Microorganisms

• Q fever: A zoonosis caused by Coxiella burnetii.
• Spotted fever: Caused by Rickettsia conorii, transmitted by dog tick bites.
• Rickettsia typhi: Transmitted through the feces of infected fleas.

Other Important Microbial Groups

• Basidiomycota: The most evolved fungi, including those that produce basidia with basidiospores.
• Ascomycota: Known as sac fungi.
• Mycoplasma pneumoniae: Colonizes the respiratory tract, mainly affecting people aged 8-30.
• Ureaplasma urealyticum: Causes non-gonococcal urethritis.
• Rickettsia typhi: The etiological agent of murine typhus.
• Mycoplasma: Small, bacteria-like organisms that are parasitic to animal or plant cells, measuring 0.3 to 0.5 mm and directly synthesizing around 750 proteins.
• Algae: Unicellular, photosynthetic microorganisms larger than bacteria, found in stagnant water, seas, rivers, and lakes.

Bacterial Appendages

• Fimbriae: Structures that link bacteria to other cells.
• Flagella: Structures responsible for movement.

Bacteria: Unicellular prokaryotes without a distinct nucleus.

Cell wall function: Gives shape to bacteria.

Algae and Their Characteristics

Algae are similar to higher plants because both microalgae and plants have chloroplasts.

Algae classification: Cyanophyta, Rhodophyta, Chlorophyta, Chrysophyta, Phaeophyta.

Chlorophyll A: Absorbs sunlight, allowing algae to convert light energy into ATP for their vital functions.

Red tides: Caused by the explosive growth of microalgae under specific conditions.

Bacterial cytoplasm: Contains DNA, ribosomes, and reserve protein granules.