As a biologist with a focus on microbiology, I can provide an in-depth explanation of why bacteria are considered living organisms. The classification of life is a complex and evolving subject, but there are several key characteristics that are generally accepted as indicators of life. These characteristics are often summarized by the acronym 'MRSGREN', which stands for Metabolism, Response, Sensitivity, Growth, Reproduction, and Energy processing, Nucleic acids, and Cellular organization. Let's delve into each of these characteristics as they apply to bacteria:

1. Metabolism: Bacteria are capable of carrying out metabolic processes. They can synthesize their own food through photosynthesis or chemosynthesis, or they can ingest organic material and break it down to obtain energy, which is a fundamental aspect of life.

2. Response: Bacteria can respond to environmental stimuli. They exhibit chemotaxis, the movement towards or away from chemicals in their environment, which is a form of response that helps them find food or avoid harmful substances.

3. Sensitivity: Bacteria are sensitive to their surroundings. They can sense changes in temperature, pressure, and chemical composition, and they can adapt to these changes, which is crucial for survival.

4. Growth: Bacteria grow and increase in size. They can take in nutrients and use them to build new cellular structures, which is a hallmark of living organisms.

5. Reproduction: Bacteria reproduce, typically through binary fission, where one cell divides into two. This is a form of asexual reproduction that is common among single-celled organisms.

6. Energy processing: Bacteria are able to convert energy from one form to another. For example, they can convert light energy into chemical energy through photosynthesis or break down organic molecules to release energy for cellular processes.

7. Nucleic acids: Bacteria contain genetic material in the form of DNA or, in some cases, RNA. This genetic material carries the instructions for the bacteria's functions and is passed on to new generations during reproduction.

8. Cellular organization: Bacteria have a cellular structure with a cell membrane, cytoplasm, and various organelles, although their cells are much simpler than those of plants and animals.

The distinction between bacteria and viruses is particularly interesting. Viruses are often not considered living organisms because they lack some of the key characteristics of life, especially outside of a host. They cannot metabolize on their own, grow, or reproduce without infecting a host cell. Once outside a host, viruses are essentially packets of genetic material that are inert. However, some argue that when viruses are inside a host and replicating, they exhibit some life-like characteristics.

It's important to note that the status of viruses as living or non-living is still a topic of debate among scientists. The question of whether viruses are alive is complex and depends on how one defines life. Some scientists argue that because viruses can evolve, reproduce (albeit only inside a host), and have genetic material, they should be considered a form of life. Others maintain that the inability to carry out life processes independently is a critical distinction that disqualifies viruses from being considered living organisms.

In conclusion, bacteria are considered living organisms because they exhibit all the key characteristics of life as we understand them. Their ability to metabolize, respond to stimuli, grow, reproduce, process energy, contain genetic material, and have cellular organization aligns with our current scientific understanding of what constitutes life. The debate surrounding viruses is a testament to the complexity and nuance of defining life, and it underscores the fact that our understanding of biology is continually evolving.

read more >>

Generally we regard bacteria as living since they are able to metabolise, respirate and excrete and divide. A virus on the other hand is not considered a living organism -if that is the right choice or word. ... Some viruses are still being questioned if they arw living or not but this is the general thought.read more >>