What is the basic structure of a bacterium?

Bacteria are the unicellular prokaryotic microorganisms. Bacteria are smallest in size and are largest in numbers among living organisms. Bacteria were first discovered by a Dutch scientist Anton van Leeuwenhoek in 1670 in rain water, then in pond water and in scraping of his teeths. He consider them as animal cules. They show some plants like characters as presence of rigid cell wall and reproduction by spores. The average size varies in micrometers as smallest one is cocci i.e. from 0.5-3.5 microns and largest is spirillum 15-22 microns. They can be rod like ( E.col, Rhizobium), spherical may be monococcus, dicoccus, streptococcus (in chain), staphylococcus( in an irregular bunch), helical, vibrio, spiral, or filamentus. Some time they are pleomorphic e.g. Acetobacter. They are chemolithotrophs or chemoautotrophs and also heterotrophs. Reproduction is either vegitative or asexual ( by conidia, or endospores). True sexual reproduction and alteration of generation are absent in bacteria, and can be done by conjugation, transformation and transduction. According to six-kingdom classification the bacteria comes under Monera i.e. of prokaryotes. According to the Cavalier-Smith two EMPIRE and eight KINGDOM classification the bacterial Empire contains two kingdoms the Eubacteria and the archaeobacteria