Functional Category Representation of Half-Life Groups
| Functional category | Experimental group | Rep. | p-value |
| Putative enzymes | HL <= 5 min | over | 6.5 × 10−5 |
| Translation and posttranslational modification | HL <= 5 min | under | 1.8 × 10−5 |
| Energy metabolism | 10 min < HL < 20 min | over | 5.4 × 10−3 |
| Translation, posttranslational modification | ORFs with measured HLs | over | 1.8 × 10−23 |
| Hypothetical, unclassified, unknown | ORFs with measured HLs | under | 1.3 × 10−8 |
| Putative transport proteins | ORFs with measured HLs | under | 2.8 × 10−5 |
[i] Several half-life groupings (HL ≤ 5 min, 5 < HL ≤ 10, 10 < HL ≤ 20, and HL > 20) were tested for over- or underrepresentation of 23 different functional categories (Blattner et al. 1997) relative to all genes whose half-lives were estimated. Categories were also identified which were over- or underrepresented in the set of all ORFs with measured half-lives. P values were calculated using the cumulative hypergeometric distribution (Tavazoie et al. 1999). A 95% confidence level was achieved using a cutoff of 2.2 × 10−3 to account for multiple hypotheses. Transcripts displaying no preference were those encoding proteins involved in transport and binding, structure and membrane proteins, carbon compound metabolism, amino acid and nucleotide biosynthesis and metabolism, and central intermediary metabolism, transcription, and posttranscriptional regulation. Despite the rapid degradation of some well studied genes (such as pnp, rhlB, and rho), as a whole, genes involved in RNA degradation were not significantly enriched in any half-life group.