1.Video Lesson

2.Objective

At the end of this lesson you will be able to:-

• Define microorganisms
• Categories microorganisms based on their morphology ,mode of nutrition, molecular and biochemical analysis
• Classify bacteria based on evolutionary, shape and nutrition
• Explain about eubacteria

Brainstorming questions

• How do structural and metabolic variations among eubacteria enable them to survive in diverse and extreme environments? Which specific adaptations, such as cell wall composition or metabolic pathways, warrant further investigation in different eubacterial groups?
• How do eubacteria contribute to nutrient cycling and the overall dynamics of ecosystems? In what ways do their interactions with other microorganisms, plants, and animals enhance ecosystem health and resilience?

key words

• Unicellular: – a unicellular organism has just one cell
• Multicellular:- an organism has more than one cell
• Microorganisms: Organisms too small to be seen clearly by the unaided eye, often requiring a microscope for observation.
• Microbiology: The study of microorganisms, including bacteria, viruses, fungi, protozoa, algae, and helminthes.
• Fungi: A group of microorganisms that include yeasts and molds, distinct from bacteria, algae, and protozoa.
• Bacteria: Unicellular, prokaryotic organisms lacking a nuclear membrane and other organelles, reproducing asexually.
• Algae: Simple, typically aquatic photosynthetic organisms, which can be unicellular or multicellular.
• Protozoa: Single-celled eukaryotic organisms, often motile and predatory, found in various environments.
• Viruses: Submicroscopic infectious agents that can only replicate within the cells of a host organism.
• Eukaryotic Microorganisms: Microorganisms with complex cells containing a nucleus and other organelles, visible without magnification.
• Domains of Life: The three major categories of life: Bacteria, Archaea, and Eukaryotes.
• Eubacteria: Also known as “true bacteria,” these are prokaryotic, unicellular organisms with no nuclear membrane and other organelles.
• Prokaryotic: Organisms, such as bacteria, lacking a nucleus and other membrane-bound organelles.
• Peptidoglycan: A complex polymer forming the cell wall of many bacteria, giving structural strength.
• Autotrophic: Organisms that produce their own food from inorganic substances, typically through photosynthesis or chemosynthesis.
• Heterotrophic: Organisms that obtain their nutrients by consuming organic substances.
• Gram Staining: A method of differentiating bacterial species into Gram-positive (retaining crystal violet dye) and Gram-negative (not retaining crystal violet dye) based on cell wall composition.
• Binary Fission: A form of asexual reproduction in bacteria where a cell divides into two genetically identical daughter cells.
• Conjugation: A form of sexual reproduction in bacteria where genetic material is transferred between cells via direct contact.
• Photoautotrophs: Autotrophs that derive their energy from sunlight.
• Chemoautotrophs: Autotrophs that obtain energy from inorganic chemical reactions.
• Photoheterotrophs: Heterotrophs that use sunlight as their energy source but require organic compounds for nutrition.
• Chemoheterotrophs: Heterotrophs that obtain energy and carbon from organic compounds.
• Morphology: The study of the form and structure of organisms, including bacteria.
• Cocci: Spherical-shaped bacteria.
• Bacilli: Rod-shaped bacteria.
• Spirochaetes: Spiral or corkscrew-shaped bacteria.
• Sex Pili: Hair-like structures on the surface of some bacteria involved in conjugation.

Microorganisms

Microorganisms are organisms too small to be seen clearly by the unaided eyes. Micro means very small-anything so small that it must be viewed with a microscope (an optical instrument used to observe very small objects). Microbiology is the study of microbes. Very small life forms so small that individual microorganisms cannot be seen without magnification.

Based on evolutionary lines, organisms are grouped into three domains that represent in figure 2. These are: –

Eubacteria (Bacteria)

Eubacteria means “true bacteria”. Bacteria are relatively simple in structure. They are prokaryotic unicellular organisms with no nuclear membrane, mitochondria, Golgi bodies, or endoplasmic reticulum that reproduce by asexual division.

General Characteristics

• They are omnipresent i.e. present in soil, air and water.
• They lack true chlorophyll, but few photosynthetic bacteria have a special type        of         chlorophyll called bacterio chlorophyll.
• They are unicellular prokaryotic microorganism.
• The cell bears a thick rigid cell wall (Peptidoglycan) outside the plasma membrane.
•  They have great variation in the mode of nutrition i.e. may be autotrophic and heterotrophic. In heterotrophic mode of nutrition, they may be parasite saprophyte or symbiotic in nature.
• Lack    true      nucleus (lacking           nuclear membrane and nucleolus).
• They lack mitochondria, Golgi apparatus, plastid and endoplasmic reticulum.
• Both DNA and RNA are present in the bacterial cell.

Structure of Bacterial Cell

Bacterial cells are very minute; they are studied under electron microscope in which it reveals various structures. Some of these are external to the cell wall while other is internal to the cell wall that show below in figure

Eukaryotics

Eukaryotic microbes are an extraordinarily diverse group, including species with a wide range of life cycles, morphological specializations, and nutritional  needs. But more diseases are caused by viruses and bacteria than by microscopic eukaryotes, these eukaryotes are responsible for some diseases of great public health importance.

 Eukaryotic microbes have eukaryotic cells that have a variety of complex membranous organelles in the cytoplasmic matrix and the majority of their genetic material within membrane-delimited nuclei. Each organelle has a distinctive structure directly related to specific functions that showed below in figure

Bacterial Shapes

Morphologically bacteria are classified based on numerous features. The criteria  used to classify bacteria within:-

• Cell shape
• Nature of multi cell aggregates,
• Motility,
• Formation of spores, and
• Reaction to the gram stain

Bacterial cells can be grouped into three main shapes, that represent in below figure

• Cocci  (singular, coccus) spherical bacteria
• Bacilli (singular, bacillus) – rod-shaped bacteria
• Spirochaetes (others like Comma-Vibrio cholera) – spiral or corkscrew-shaped bacteria

In other ways bacteria classified based on their cell wall composition. These structure retaining dyes during Gram’s stain, Due to this bacterium can be categorized into two: –

• Gram-positive bacteria
• Gram-negative bacteria

Gram-positive bacteria

These bacteria   have a distinctive purple appearance when observed under a light microscope in Gram staining. This   is due to retention of the purple crystal violet stain in the thick peptidoglycan layer of the cell wall

• Eg.All staphylococci,
•        All streptococci and
•       Some listeria species.

Gram negative bacteria

These bacteria lose the crystal violet stain and take the color of the red counter stain in Gram- staining, Due have a cell wall composed of a thin layer of peptidoglycan

Gram staining

Gram staining is a method used to classify bacteria into two groups based on the structural differences in their cell walls.The Gram staining process includes four basic steps, including:

Nutritional types of bacteria

Bacteria use different mechanisms to acquire the energy and nutrients they need for growth and reproduction. Based on the way of getting energy, it can be grouped as follow: –

• Autotrophs
• Heterotrophs

Autotrophic bacteria

is a bacterium that prepare their own foods from inorganic molecules and water. These bacteria also grouped into:-

• Photoautotroph
• Chemoautotroph

Autotrophs that obtain their energy from sunlight are called photoautotrophs, while those that harvest energy from inorganic chemicals are called chemoautotrophs

Heterotrophic bacteria

Those organisms that obtain at least some of their carbon from organic molecules like glucose. these includes:-

• Photoheterotrophs
• Chemoheterotrophs

Heterotrophs can be classified based on their energy sources. Photoheterotrophs derive energy from sunlight, while chemoheterotrophs obtain it from organic molecules. Energy sources for nutrition include light and the oxidation of organic or inorganic molecules. Phototrophs use light for energy, and chemotrophs rely on chemical compound oxidation. Bacteria obtain electrons from either inorganic substances (lithotrophs) or organic compounds (organotrophs). Despite their metabolic diversity, most bacteria fall into five nutritional classes, primarily being photolithoautotrophic or chemoorganoheterotrophic

Photolithoautotrophs

photoautotrophs use light energy and have CO2 as their carbon source. Photosynthetic bacteria and cyanobacteria employ water as the electron donor and release oxygen. Other photolithoautotrophs, such as the purple and green sulfur bacteria, cannot oxidize water but extract electrons from inorganic donors such as hydrogen, hydrogen sulfide, and elemental sulfur.

Chemo organoheterotrophs

Sometimes called chemoheterotrophs or chemoorganotrophs use organic compounds as sources of energy, hydrogen, electrons, and carbon. All pathogenic microorganisms are chemoorganoheterotrophs. Some photosynthetic bacteria (purple and green bacteria) use organic matter as their electron donor and carbon source. These Photoorganoheterotrophs are common inhabitants of polluted lakes and streams. Some of these bacteria also can grow as photolithoautotrophs with molecular hydrogen as an electron donor.

Chemolithoautotrophs oxidize reduced inorganic compounds such as iron, nitrogen, or sulfur molecules to derive both energy and electrons for biosynthesis. Carbon dioxide is the carbon source.

Chemolithoheterotrophs use reduced inorganic molecules as their energy and electron source but derive their carbon from organic sources. Chemolithotrophs contribute greatly to the chemical transformations of elements (e.g., the conversion of ammonia to nitrate or sulfur to sulfate) that continually occur in ecosystems.

Reproduction in bacteria

Like other organisms bacteria can be reproduced. There are two mechanisms of reproduction in bacteria. These are:-

• Asexual reproduction
• Sexual reproduction

Asexual reproduction

Most bacterial organisms reproduce by an asexual process called binary fission, which usually occurs after a period of growth in which the cell doubles in mass. At this time, the chromosome (DNA) replicates and the two DNA molecules separate. Chromosome segregation is not well understood. Unlike eukaryotic cells, bacterial cells lack a mitotic spindle to separate replicated chromosomes.

Sexual reproduction

Bacterial sexual reproduction is known as conjugation. During conjugation, two bacterial cells of different mating types connect, allowing genetic material to be transferred from one cell to the other. This process requires direct contact between the two cells.

Common bacterial diseases