Taxonomy: Kingdom Monera

Kingdom Monera contains one-celled or unicellular organisms. A moneran cell has a cell wall, a cell membrane, and a cytoplasm. It has no nucleus and no organelles. But like other organisms, moneran cells perform the basic life process. They grow, reproduce, and break down food to provide energy.

Monerans are the oldest, the simplest and the most abundant organisms on earth.  Because they are the only organisms that lack a membrane-bound nucleus (prokaryotic), they are named monera, which means alone.  Monerans lack most of the organelles that other cell have.  They exist a single cell and are very small.  Their sizes range from 1 to 10 micrometers.  Thus, they are visible only under a microscope.  Monerans are grouped into two:   bacteria and cyanobacteria.

Two Groups of Kingdom Monera

1. Bacteria are perhaps the more familiar of the two groups of moneran. They live everywhere. Bacteria can be found in the soil, in the water, in the air we breathe, in the milk we drink, on our skin, and even inside our body. Many bacteria grow very well at temperatures close to the human body, 37˚C. But some types of bacteria can survive in extreme temperatures. They can live at temperatures below 0˚C. Others can live at high temperatures like in hot springs where temperatures may reach about 100˚C.

Bacteria are grouped into three according to their shapes.

• Spherical or round-shaped bacteria called cocci.
• Rod-shaped bacteria called bacilli.
• Spiral-shaped bacteria are called spirilla.

Bacteria may also form colonies. For, example, a pair of cocci is called diplococcus, a chain is called streptococcus, and a cluster is called staphylococcus. Similarly, a pair of bacilli is called diplobacilli and a chain is called streptobacilli.

Bacteria may be aerobic (need oxygen to survive) or anaerobic (can live without oxygen). They reproduce asexually by means of binary fusion. Binary fusion involves the replication of the DNA and the division of the cytoplasm, followed by the splitting of the bacterial cell into two. This is similar to mitotic division in eukaryotic cells.

Beneficial Bacteria

Contrary to what most people believe, most bacteria are not harmful. Bacteria have become extremely important in our lives for the following reasons:

1. Bacteria are decomposers or agents of decay. They use dead organisms, sewage, and other wastes as source of food and energy, thereby recycling the nutrients so that they are made available for use in the biosphere. Without the bacteria and the other decomposers, our world would have become a huge heap of wastes.

2. Some bacteria, such as Burkholderia cepacia, can break down crude oil into simpler substance that serves as food for aquatic organisms. These oil-eating bacteria are used in recycling and cleaning up oil spills.

3. Bacteria are used in many industries for the processing of food such as cheese, yogurt, nata de coco, and vinegar. Medicines, enzymes, cleansers, adhesives, alcohols, acetones, and other products are also produced through bacterial cultures.

4. Nitrogen-fixing bacteria in the roots of leguminous plants, such as peanuts and peas, enrich the soil by absorbing the nitrogen from the atmosphere and converting it to usable forms, such as nitrites and nitrates. These are used by plants in making nitrogen compounds. Animals and humans also benefit because they obtain from plants the nitrogen they need to produce proteins.

5. Photosynthetic bacteria increase oxygen in the atmosphere. They also provide oxygen to aquatic organisms.

6. Some bacteria that thrive in the intestines of animals and humans produce antibiotics that prevent the growth of disease-causing bacteria and compete with them for food, thereby controlling their population. They aid in digestion by releasing various nutrients. They also produce and release vitamin k.

Harmful Bacteria

While most bacteria benefit humans, some are known to be the major causes of diseases. Bacteria that cause infectious diseases are called pathogens. Bacteria can invade the healthy tissues of their host and cause disease by altering the normal functions of the tissues. Bacterial illness are caused by various enzymes or toxins produced by the bacteria. They may be ingested with food and drink, or released by the bacteria while inside the host tissue. Botulism, for example, is a type of food poisoning caused by toxins released by the bacterium, Clostridium botulinum. Cause paralysis and death. It usually thrives in improperly processed canned foods. It is able to grow in canned foods because it is anaerobic, meaning, it does not require oxygen in order to survive. Botulism toxins can be destroyed by heating the food. Pneumonia, tuberculosis, strep throat, and leprosy are caused by enzymes released by bacteria while inside the host, while tetanus is caused by bacterial toxins.

Cyanophyta: Food-producing Bacteria

Most members of cyanophyta contain chlorophyll and a blue pigment, whose combination gives it the blue-green color. They were formerly known as blue-green algae due to their resemblance to microscopic algae. However, due to the absence of membrane-bound nucleus, they were reclassified as monerans.

They are now more appropriately called the blue-green bacteria. Not all cyanobacteria, however, are blue-green. Some are red, yellow, or black. Cyanobacteria produce food through photosynthesis. They provide nutrition for freshwater fishes.

Tags: classification of living things, kingdom, kingdom monera, kingdom of living things, levels of cla, modern taxonomy, taxonomy

Category: Biology