fold change for rna seq data without replicates

[Francy87]

Hi all!
I have bacterial metatranscriptome from 12 samples but I don't have any biological replicates. They are a time serie (1 sample for each time point).

I know that for differential expression analysis I would need replicates, but at the moment we can't afford that.

I'd like at least to be able to say if there is a higher or lower expression of some genes during the time.

Anyone can suggest me how to proceed?
How can I normalize the gene counts for sequencing depth and calculate which genes are up or down-regulated between each couple of samples?

Thanks a mil
francesca