2.1.2. Eubacteria

There are thousands of different eubacteria or ‘true bacteria’. They are characterised by the presence of a rigid cell wall, and if motile, a flagellum.

Eubacteria, often referred to as 'true bacteria', form a large group of single-celled organisms. They are differentiated from other types of bacteria primarily by their structural characteristics, such as having a rigid cell wall. Additionally, if they have the ability to move, they possess a structure known as a flagellum, which acts like a tail to help them swim and navigate their environment.

Think of eubacteria like tiny boats (the bacteria) with sails (the flagella) that allow them to navigate through water (their environment). Just like boats that are built with solid hulls (the rigid cell wall), eubacteria have a strong outer layer that helps maintain their shape and protects them.

The cyanobacteria (also referred to as blue-green algae) have chlorophyll a similar to green plants and are photosynthetic autotrophs. The cyanobacteria are unicellular, colonial or filamentous, freshwater/marine or terrestrial algae.

Cyanobacteria, often called blue-green algae, are a specific group of eubacteria known for their ability to perform photosynthesis, much like plants. They contain chlorophyll a, which allows them to capture sunlight and convert carbon dioxide and water into glucose and oxygen. These organisms can exist as single cells (unicellular), in colonies, or as long filaments. They thrive in various environments, including freshwater, marine, and even terrestrial areas.

Imagine a vibrant pond filled with green plants. The presence of cyanobacteria in the water not only adds to the color but also helps produce oxygen, much like a group of friends working together to grow a beautiful garden where each plant plays its role.

The colonies are generally surrounded by gelatinous sheath. They often form blooms in polluted water bodies. Some of these organisms can fix atmospheric nitrogen in specialised cells called heterocysts, e.g., Nostoc and Anabaena.

Cyanobacterial colonies are often encased in a jelly-like substance, providing them protection and structural support. In environments with excess nutrients, such as polluted waters, these organisms can multiply rapidly, causing what is known as a 'bloom.' Notably, certain cyanobacteria can fix nitrogen, transforming nitrogen gas from the air into a usable form for plants. This process occurs in special cells called heterocysts, found in genera like Nostoc and Anabaena.

Think of cyanobacteria like a community garden in a neighborhood that has been neglected and polluted. When they flourish (bloom), they can actually clean up some of the mess (like fixing nitrogen), making the environment better for surrounding plants and animals.

Chemosynthetic autotrophic bacteria oxidise various inorganic substances such as nitrates, nitrites and ammonia and use the released energy for their ATP production.

Chemosynthetic autotrophic bacteria are another fascinating group of eubacteria that do not rely on sunlight for energy. Instead, they obtain energy by oxidizing inorganic substances, like nitrates, nitrites, or ammonia. This energy is then used to produce ATP (adenosine triphosphate), the energy currency of cells, enabling them to thrive in environments where sunlight is scarce.

Imagine living in a dark cave where there’s no sunlight. Instead of plants, you rely on certain minerals found in the cave walls to get your energy, similar to how these bacteria survive. They essentially become the energy providers in dark environments, just like plants do in sunlight.

Heterotrophic bacteria are most abundant in nature. The majority are important decomposers. Many of them have a significant impact on human affairs.

Heterotrophic bacteria play a crucial role in ecosystems as they rely on other organic matter for their nutrition. These bacteria are the primary decomposers in nature, breaking down dead plants and animals and recycling nutrients back into the environment. This process is vital for maintaining ecological balance. Their activities greatly influence human activities, such as in food production processes, including fermentation, and in medical fields through antibiotic production.

Think of heterotrophic bacteria as nature's clean-up crew. They break down waste and dead material, allowing new life to flourish, just like a team of volunteers cleaning up a park brings it back to life for everyone to enjoy.

Some are pathogens causing damage to human beings, crops, farm animals and pets. Cholera, typhoid, tetanus, citrus canker are well known diseases caused by different bacteria.

While many eubacteria are beneficial, some are pathogenic, meaning they can cause diseases in humans, animals, and plants. Certain types of bacteria can lead to serious illnesses such as cholera, typhoid fever, tetanus, and citrus canker disease. This highlights the dual role of bacteria: they can be both harmful and helpful.

Consider how certain bacteria can act like uninvited guests at a party, causing chaos and destruction. Just as a party can be ruined by some rowdy guests, our health can be negatively impacted by pathogenic bacteria.

Bacteria reproduce mainly by fission. Sometimes, under unfavourable conditions, they produce spores. They also reproduce by a sort of sexual reproduction by adopting a primitive type of DNA transfer from one bacterium to the other.

Bacteria primarily reproduce through a process called binary fission, where one bacterium divides into two. This method allows for rapid population growth. Under unfavorable conditions, some bacteria can form spores, which are resistant forms that can survive harsh conditions. Additionally, bacteria can exchange genetic material through a primitive form of sexual reproduction called horizontal gene transfer, which allows for genetic diversity.

Imagine a factory producing identical toys. In any situation where the production line breaks down (unfavorable conditions), some toys might be set aside to protect them until production resumes (spores). Meanwhile, occasionally, the factory might share ideas with another factory to create improved toys (genetic transfer), making the entire production process more efficient.

The Mycoplasma are organisms that completely lack a cell wall. They are the smallest living cells known and can survive without oxygen.

Mycoplasma is a unique group of bacteria notable for lacking a cell wall, which makes them highly flexible and capable of adopting various shapes. They are the smallest known living cells and can survive in quick changing environments, even without oxygen. This adaptation makes them distinct and often pathogenic in some cases, affecting both animals and plants.

Think of mycoplasma as the agile gymnasts of the microbial world. Without a rigid structure (cell wall), they can twist and turn through life with ease, maneuvering around challenges where other bacterial types might struggle to survive.

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