The Eternal Struggle

At t = 0, Bio Man placed eight living cells on an irregularly-shaped grid. Over the course of the next 13 seconds, each square of the grid was occupied by a live cell for at least one second; at t = 14, shown below, was the first time the cells moved beyond the boundaries of the grid.

As it happens, many of the squares in this grid also contain letters! But at any given time only the letters in grid squares occupied by live cells are visible. Below is a list of what letters were visible at each second before the cells began to escape the grid. (Letters are sorted from left to right by columns—i.e., in the order in which you would see them reading down the first column, then down the second column, etc.)