Different Size, Shape and Arrangement of Bacterial Cells!!!

Bacteria are prokaryotic, unicellular microorganisms, which lack chlorophyll pigments. The cell structure is simpler than that of other organisms as there is no nucleus or membrane bound organelles. Due to the presence of a rigid cell wall, bacteria maintain a definite shape, though they vary as shape, size and structure.

When viewed under light microscope, most bacteria appear in variations of three major shapes: the rod (bacillus), the sphere (coccus) and the spiral type (vibrio).

In fact, structure of bacteria has two aspects, arrangement and shape. So far as the arrangement is concerned, it may Paired (diplo), Grape-like clusters (staphylo) or Chains (strepto). In shape they may principally be Rods (bacilli), Spheres (cocci), and Spirals (spirillum).

Shape of Bacterial Cells

• Cocci (or coccus for a single cell) are round cells, sometimes slightly flattened when they are adjacent to one another.

• Bacilli (or bacillus for a single cell) are rod-shaped bacteria.

• Spirilla (or spirillum for a single cell) are curved bacteria which can range from a gently curved shape to a corkscrew-like spiral. Many spirilla are rigid and capable of movement. A special group of spirilla known as spirochetes are long, slender, and flexible.

Size of Bacterial Cell

The average diameter of spherical bacteria is 0.5-2.0 µm. For rod-shaped or filamentous bacteria, length is 1-10 µm and diameter is 0.25-1 .0 µm.

Thus a few bacteria are much larger than the average eukaryotic cell (typical plant and animal cells are around 10 to 50 µm in diameter).

Below is a list of various bacteria and sizes.

You do not have to read this portion:

• E. coli , a bacillus of about average size is 1.1 to 1.5 µm wide by 2.0 to 6.0 µm long.

• Spirochaetes occasionally reach 500 µm in length and the cyanobacterium

• Oscillatoria is about 7 µm in diameter.

• The bacterium, Epulosiscium fishelsoni , can be seen with the naked eye (600 µm long by 80 µm in diameter).

• One group of bacteria, called the Mycoplasmas, have individuals with size much smaller than these dimensions. They measure about 0.25 µ and are the smallest cells known so far. They were formerly known as pleuropneumonia-like organisms (PPLO).

• Mycoplasma gallicepticum, with a size of approximately 200 to 300 nm are thought to be the world smallest bacteria.

• Thiomargarita namibiensis is world’s largest bacteria, a gram-negative Proteobacterium found in the ocean sediments off the coast of Namibia. Usually it is 0.1—0.3 mm (100—300 µm) across, but bigger cells have been observed up to 0.75 mm (750 µm).

Beneficial, harmful, and opportunistic bacteria

Typical intestinal bacteria are classified according to their actions into three types.

Good bacteria have health maintenance and anti-aging effects such as aiding digestion and absorption, and stimulating immunity. Representative examples are bifidobacteria and lactic acid bacteria.

In contrast, bad bacteria have adverse effects on the body. Representative examples include Clostridium perfringens, Staphylococcus, and Escherichia coli (E. coli; toxic strain). They inhibit health by triggering disease and promoting aging.

Opportunistic bacteria cause no trouble when you are healthy, but have adverse effects upon the intestines when the body is weak. Representative examples include Bacteroidetes, E. coli (nontoxic strain), and Streptococcus.

Changes in intestinal bacteria with age

Bacterial groups in the intestines change with age-the percentage of bad bacteria increases as you grow older.

A fetus in the womb is kept in a sterile environment.

When the baby drinks breast milk, bifidobacteria start to grow, using the lactose and galactooligosaccharides in breast milk as a source of nutrition. A baby's stool is yellowish and does not smell because its intestinal environment is dominated by bifidobacteria.

The weaning period is when babies are slowly taken off of breats milk and start to eat smashed food. From the weaning period onwards, bacterial flora change to that of an adult as the baby starts to eat baby food. In adults, bifidobacteria account for 10-20% of intestinal bacteria.

In most elderly, bifidobacteria will have decreased in most cases and bad bacteria such as clostridium perfringens, which are not detected in youth, have a high probability of being detected.

Balance of bacteria

The balance of good bacteria, bad bacteria and opportunistic bacteria changes with physical condition and age. For maintaining good health, it is necessary to create a healthy intestinal environment with good bacteria.