Book:Bacteria

Introduction

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometers in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of the Earth's crust. Bacteria also live in symbiotic and parasitic relationships with plants and animals.

Structure and Function

Bacteria are unicellular organisms that lack a nucleus and membrane-bound organelles. Their genetic material is usually a single circular chromosome located in the nucleoid. Bacteria have a cell wall that provides structural support and protection. The composition of the cell wall varies between different types of bacteria and is a key factor in the classification of bacteria into Gram-positive and Gram-negative groups.

Cell Wall

The cell wall of bacteria is crucial for maintaining the shape of the cell and protecting it from osmotic pressure. In Gram-positive bacteria, the cell wall is thick and consists mainly of peptidoglycan. In contrast, Gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane containing lipopolysaccharides.

Reproduction

Bacteria primarily reproduce through a process called binary fission, where a single cell divides into two identical daughter cells. This process can occur rapidly, allowing bacterial populations to grow quickly under favorable conditions.

Metabolism

Bacteria exhibit a wide range of metabolic capabilities. They can be classified based on their energy and carbon sources:

• Phototrophs obtain energy from light.
• Chemotrophs obtain energy from chemical compounds.
• Autotrophs use carbon dioxide as their carbon source.
• Heterotrophs require organic carbon sources.

Role in the Environment

Bacteria play a vital role in the environment, including:

• Decomposition: Bacteria break down dead organic matter, recycling nutrients back into the ecosystem.
• Nitrogen Fixation: Certain bacteria convert atmospheric nitrogen into forms usable by plants.
• Bioremediation: Bacteria can degrade pollutants, aiding in environmental cleanup efforts.

Medical Importance

Bacteria can be both beneficial and harmful to human health. Beneficial bacteria, such as those in the human gut microbiota, aid in digestion and protect against pathogens. However, pathogenic bacteria can cause diseases such as tuberculosis, cholera, and pneumonia.

Also see

• Antibiotic resistance
• Microbiome
• Prokaryote
• Virus