| Finding/Claim | Evidence type | Key quantitative details | Conditions/strain | Interpretation/notes | Primary citation (include DOI/URL and year) |
|---|---|---|---|---|---|
| **mbiA/htgA is the same E. coli K-12/O157:H7 overlapping gene as UniProt P28697 (b0012), completely antisense to yaaW** | Genomic mapping, annotation review, promoter/TSS study | htgA/mbiA is described as completely embedded antisense within **yaaW** and located upstream of **dnaK**; later proposed rename to **mbiA** (“modifier of biofilm”) | E. coli O157:H7 EDL933 in the primary experimental paper; orthologous locus corresponds to K-12 b0012/P28697 | Supports correct target identification and warns against confusing htgA/mbiA with unrelated symbols in other organisms; overlapping architecture is central to interpretation of all mutant data (pqac-00000004, pqac-00000009) | Fellner et al., 2014, *FEMS Microbiol Lett* 350:57-64, DOI: 10.1111/1574-6968.12288, https://doi.org/10.1111/1574-6968.12288 (pqac-00000004, pqac-00000009) |
| **Likely start codon is GTG rather than annotated rare CTG; predicted size ~174 aa** | ORF analysis with strand-specific mutagenesis design | Annotated start codon is a rare **CTG**; authors state the next **GTG** is more likely; counting from GTG gives **525 bp / 174 aa** | E. coli O157:H7 EDL933 mutant design | Indicates protein is small and start-site assignment remains uncertain; this uncertainty may contribute to poor detection of HtgA/MbiA protein (pqac-00000000, pqac-00000008) | Fellner et al., 2014, DOI: 10.1111/1574-6968.12288, https://doi.org/10.1111/1574-6968.12288 (pqac-00000000, pqac-00000008) |
| **Both strands show transcription-related features, but yaaW and htgA are not expression synonyms** | Promoter::gfp fusion, 5′-RACE, terminator prediction, transcriptomics | htgA major TSS mapped **135 bp upstream**; prior reports/predictions placed sites **82/98/114 bp** upstream; yaaW major TSS mapped **32 bp upstream of yaaI**, with a minor site **107 bp upstream of yaaW**; htgA upstream region showed promoter activity; yaaI promoter active while yaaW-alone region resembled empty vector; no terminator directly downstream of htgA, terminator predicted downstream of dnaK | E. coli O157:H7 EDL933; reporter assays in LB and 5′-RACE under condition-specific growth setups | Suggests htgA is genuinely transcribed, albeit weakly/conditionally; also indicates yaaW may be within an operon and that database synonymization of htgA with yaaW is misleading (pqac-00000000, pqac-00000003, pqac-00000008, pqac-00000009) | Fellner et al., 2014, DOI: 10.1111/1574-6968.12288, https://doi.org/10.1111/1574-6968.12288 (pqac-00000000, pqac-00000003, pqac-00000008, pqac-00000009) |
| **YaaW protein was detected, but HtgA/MbiA protein was not detected in the same overexpression/Western setup** | Heterologous expression, Ni-NTA purification, anti-myc Western blot; comparison with prior radiolabeling study | **YaaW ~30 kDa** detected on Western blot; **no HtgA band** detected; earlier study reported a putative **~21 kDa** htgA product by **35S labeling**, described as more sensitive | Overexpression in EHEC/EDL933 with myc-His tag fusion | Strongly suggests HtgA/MbiA is hard to detect and may be unstable or low abundance; absence on Western blot does **not** rule out translation (pqac-00000000, pqac-00000008, pqac-00000011) | Fellner et al., 2014, DOI: 10.1111/1574-6968.12288, https://doi.org/10.1111/1574-6968.12288; earlier study cited therein: Missiakas et al., 1993 (pqac-00000000, pqac-00000008, pqac-00000011) |
| **No detectable growth or heat-shock phenotype in strand-specific single mutants** | Genetic mutant phenotype; growth curves | No growth difference at **37°C**; no difference after **30→45°C upshift**; prior heat-shock annotation could not be confirmed | E. coli O157:H7 EDL933 ΔhtgA and ΔyaaW single-gene stop mutants | The historical name **htgA** (“high-temperature growth”) is not supported by later targeted experiments; current best phenotype is biofilm modification, not heat tolerance (pqac-00000000, pqac-00000006, pqac-00000008, pqac-00000010) | Fellner et al., 2014, DOI: 10.1111/1574-6968.12288, https://doi.org/10.1111/1574-6968.12288 (pqac-00000000, pqac-00000006, pqac-00000008, pqac-00000010) |
| **Primary phenotype is increased biofilm formation when mbiA/htgA is disrupted** | Genetic mutant phenotype; crystal-violet biofilm assay | Both **ΔhtgA** and **ΔyaaW** showed increased biofilm, especially after **48 h at 37°C** in minimal medium; earlier K-12 work reported **~3-fold increase** for the **double htgA/yaaW mutant** after biofilm growth | EDL933 single mutants in M9 minimal medium; prior K-12 double mutant comparison cited by authors | This is the main experimentally supported functional clue and motivated renaming **htgA → mbiA (modifier of biofilm)**; however, the biochemical mechanism remains unresolved (pqac-00000000, pqac-00000001, pqac-00000006, pqac-00000008, pqac-00000010) | Fellner et al., 2014, DOI: 10.1111/1574-6968.12288, https://doi.org/10.1111/1574-6968.12288; cites Domka et al., 2007 for K-12 double mutant phenotype (pqac-00000000, pqac-00000001, pqac-00000006, pqac-00000008, pqac-00000010) |
| **Loss of mbiA/htgA alters the metabolome despite no growth defect** | Untargeted metabolomics (ICR-FT/MS) | **22 metabolites** significantly changed overall (**P ≤ 0.01**); comparisons: **ΔhtgA vs WT = 4**, **ΔyaaW vs WT = 14**, **ΔhtgA vs ΔyaaW = 4**; in both mutants, changed metabolites were **decreased** relative to WT; changes mainly linked to **fatty acid** or **amino acid metabolism** | EDL933 ΔhtgA, ΔyaaW, WT | Supports biological functionality of both overlapping reading frames; suggests influence on metabolism but not a defined enzymatic role/pathway (pqac-00000001, pqac-00000006) | Fellner et al., 2014, DOI: 10.1111/1574-6968.12288, https://doi.org/10.1111/1574-6968.12288 (pqac-00000001, pqac-00000006) |
| **mbiA/htgA is taxonomically restricted and likely under purifying selection in a subset of enteric lineages** | Comparative genomics and overlapping-gene evolutionary analysis | Full-length htgA found only in **Escherichia** and **Shigella**; in **Salmonella**, htgA is a **pseudogene** and disrupted at the same positions; yaaW divergence is low (**max 2.6% amino acid level** in cited comparison); htgA inferred under purifying selection in at least **24 strains** of Escherichia/Shigella | Comparative analysis across Enterobacterales/Gammaproteobacteria | Best viewed as a **young orphan/lineage-specific overlapping gene** rather than a conserved housekeeping protein; this also explains sparse annotation and limited literature (pqac-00000002, pqac-00000004, pqac-00000007) | Fellner et al., 2014, DOI: 10.1111/1574-6968.12288, https://doi.org/10.1111/1574-6968.12288 (pqac-00000002, pqac-00000004, pqac-00000007) |
| **Expression is condition responsive in transcriptome datasets, including biofilm-associated induction** | Microarray/database mining (GENEXPDB Table 1 excerpt) | Reported htgA fold changes include **2.62** in biofilm (**15 h vs 4 h**), **6.043** with **100 µg bicyclomycin** in strain **MDS42**, **4.7** with **100 µg bicyclomycin** in **MG1655**, and **2.056** after **1 h UV**; corresponding yaaW values were lower or opposite in some cases (e.g., **1.649** in biofilm, **0.567/0.442** with bicyclomycin) | Multiple E. coli strains/conditions compiled in GENEXPDB | Supports regulated expression and further argues htgA and yaaW should not be treated as synonyms; however, these are indirect expression data and not proof of protein function (pqac-00000003, pqac-00000008) | Fellner et al., 2014 Table 1 / GENEXPDB excerpt, DOI: 10.1111/1574-6968.12288, https://doi.org/10.1111/1574-6968.12288 (pqac-00000003, pqac-00000008) |
| **Recent understanding still emphasizes mbiA/htgA as a rare bacterial antisense overlapping gene with limited direct mechanistic characterization** | Review/commentary and methodological literature | Later literature cites htgA/mbiA as an example of a functional antisense overlapping gene; no new 2023-2024 direct mechanistic study on E. coli K-12 b0012 was found in this session | Reviews/methods papers on antisense proteins and ribosome profiling | Current evidence supports phenotype and evolutionary plausibility, but direct molecular function, localization, domains, and interaction partners remain unresolved; literature is limited and should not be extrapolated to unrelated genes with similar symbols (pqac-00000005) | Glaub et al., 2020, *J Biol Chem* 295:8999-9011, DOI: 10.1074/jbc.RA119.012161, https://doi.org/10.1074/jbc.RA119.012161; cites Fellner et al. 2014 as key case study (pqac-00000005) |


*Table: This table summarizes the main experimentally supported findings for E. coli mbiA/htgA (UniProt P28697; b0012), including genomic context, transcription, phenotypes, metabolomics, and evolutionary evidence. It is useful as a concise evidence map for what is known versus still unresolved about this poorly characterized overlapping gene.*