Why would a bacterial population show initial growth when it is in unfavorable growth conditions?
E. faecalis is an aerotolerant anaerobe, while E. coli is a facultative anaerobe therefore if in a non-aerobic environment it can switch to anaerobic respiration. E.coli is also capable of fermentation.

Here is an article for on the various respiratory pathways of E.coli: http://www.sciencedirect.com/science/article/pii/S0005272897000340

One other reasons why cells may grow in a nutrient poor medium is that many types of bacteria have programmed cell death that ultimately is for the better of the entire bacterial population. When nutrients get low some cells commit "suicide" and release nutrients to surrounding bacteria. Just an extra thought.