Bacterial colony
= Bacterial colony
A <bacterial colony> is a spatially localized population of <bacteria> growing together. On a suitable solid <culture medium>, growth can produce a visible patch containing many <cells>. The patch, its constituent <cells> and the lineage that produced them are different things to measure.
For an original ideal lineage calculation, assume one founder, exactly one <binary fission> per generation, no cell loss and no merging with another population. After $n$ generations the population is $2^n$; after 20 generations it is 1,048,576 <cells>. This explains how one localized growth origin can produce many <cells>. The founding-cell assumption is not established simply by observing the final patch's outline.
A colony also has physical organization. In a 2008 experiment, <Escherichia coli> grew in a <microfluidics>-based <chemostat>. As the population became dense and expanded, rod-shaped <cells> developed orientational alignment with the flow. Imaging and mechanical models connected <cell division> and contact forces with a collective pattern.<Biomechanical ordering of dense cell populations by Dmitri Volfson and others>[Abstract and Figure1: confined population growth, expansion flow and orientational alignment]{ref}
Colony size, cell number and cell arrangement therefore answer different questions. Two equally populated colonies could occupy different areas if they differ in packing or grow in different numbers of layers. Conversely, two equal visible areas need not contain equal numbers of viable <cells>. A defined counting method and a defined spatial measurement are needed to make either comparison.