Chapter one: the evolution of microoorganisms and microbiology. Microorganisms: organisms/acellular biological entities too small to be seen clearly by unaided eye. Macroscopic microbes are often colonial consisting of small aggregation of cells. Prokaryotic cells: co(cid:374)te(cid:374)ts a(cid:396)e(cid:374)"t divided i(cid:374)to (cid:272)o(cid:373)pa(cid:396)t(cid:373)e(cid:374)ts (cid:271)(cid:455) (cid:373)e(cid:373)(cid:271)(cid:396)a(cid:374)es, la(cid:272)k (cid:373)e(cid:373)(cid:271)(cid:396)a(cid:374)e-delimited nucleus. Eukaryotic cells: have an nucleus and many other membrane-bound organelles that separate some cellular materials and processes from others. Microorganisms (except for viruses and acellular infectious agents) placed in kingdoms: monera, protista, fungi. All organisms with prokaryotic cell structure placed in monera. Comparison of ribosomal rna showed two different groups of organisms with prokaryotic cell architecture, bacteria and archaea. Cellular organisms divided into three domains: bacteria, archaea and eukarya. Bacteria: usually single celled, most have cell walls that contain peptidoglycan. Exhibit prokaryotic cell structure and breaks down dead plants/animals. Archaea: distinctive rrna sequences, lack of peptidoglycan in cell walls, unique membrane lipids, found in extreme environments.