Explain the largest group of bacteria Eubacteria?

Eubacteria are the largest group of bacteria within Kingdom Monera. They are the "true" bacteria, what most people referred to when they spoke of bacteria prior to the inclusion of the blue-green bacteria and the recognition of the archaebacteria species. Like all members of Kingdom Monera, eubacteria are prokaryotes, which means that they lack an organized nucleus and other double-membraned organelles such as ER, mitochondria, chloroplasts, and Golgi apparatus. They are also relatively small in size, compared to eukaryotic cells, ranging from 1 to 10 micrometers.

Eubacteria have cell walls outside of their cell, or plasma, membranes. These cell walls are made of a complex sugar, rather than the cellulose material which forms plant cell walls. Different types of bacterial cell walls can be distinguished from one another by their ability to take up a stain known as the Gram Stain. Some species of bacteria also produce a protective gelatinous capsule outside the cell wall, enabling the cells to stick to surfaces.

Approximately half of the eubacteria species move in one of three ways: using flagellae, filaments, or secreting slimy chemicals that enable sliding or gliding.

There are 3 basic shapes of bacteria: rod-shaped bacilli, spherical cocci, and spiral-shaped spirilla, or spirochaetes.
Solitary coccoid bacteria are called monococci. Sometimes two coccoid bacteria grow in pairs, and these are referred to as diplococci.If they grow in grape-like clusters, they are known as staphylococcus, and if they appear in chains, they are then called streptococcus. You may have heard people speak of "staph," or "strep" infections!

have been very successful over the years - about 3.5 billion years, more or less! Besides having evolved into very diverse organisms structurally, they also have evolved many different types of life styles. There are bacteria that are autotrophic - that is to say, they feed themselves. Autotrophic bacteria can be photosynthetic - taking energy from sunlight (Cyanobacteria or photosynthetic eubacteria) or chemotrophic - which means they derive energy from inorganic chemicals. There are other bacteria that are heterotrophic - they break down organic substances and absorb the smaller molecules. Just think of food that has been left out too long and has spoiled! Another unusual group of bacteria are the photoheterotrophs. These unique bacteria require organic nutrients in addition to energy derived from photosynthesis.

Bacteria carry on cellular aerobic respiration as well as anaerobic respiration. That is, some bacteria require oxygen to sustain life - these are called obligate aerobes.

Other species of bacteria require an absence of oxygen to survive, and are called obligate anaerobes. A well-known obligate anaerobe is Clostridium botulinum, the bacteria that causes botulism. In a closed airtight container of food, Clostridium botulinum produces a deadly toxin that can cause paralysis or even death. Another infamous obligate anaerobe is Clostridium tetani, which upon entering a deep wound where there is limited oxygen, produces another toxin leading to tetanus - a prolonged, painful contraction of muscles.
A third group of bacteria has the ability to survive in either the presence or the absence of oxygen. These are referred to as facultative anaerobes.

Bacteria, being prokaryotes, lack an organized nucleus, and so do not reproduce through either mitosis or meiosis. Instead, they reproduce by binary fission. Several types of bacteria are able to produce endospores when adverse conditions occur. These are highly resistant to lack of nutrients and water, and are also tolerant of extreme temperatures.

While these abilities have helped bacteria to survive over the ages, they also present a problem to humans, who often need to store food over periods of time. Since bacteria double in number every time they reproduce, large numbers of cells can build up in a relatively short span of time. Thus, we need to ensure that there are no living bacteria in food which must be stored for extended periods of time, either by cooking it thoroughly, or by subjecting it to high heat and pressure. Short term storage of food is usually accomplished through refrigeration or drying.