| Claim/Observation | Evidence type (microscopy, genetics, biochemistry, review) | Quantitative details | Experimental system | Interpretation for function/localization | Primary source (authors, year, journal) | URL |
|---|---|---|---|---|---|---|
| T4 **ndd** encodes the protein responsible for early host nucleoid (“nuclear”) disruption and matches the UniProt description of a nucleoid disruption protein | Genetics, sequence analysis | Predicted protein size **~16.9 kDa**; earlier infection studies detected an absent band of **~15 kDa** in **ndd** mutants | Enterobacteria phage T4 infecting *E. coli*; mutant mapping and sequencing | Supports annotation of P15556 as the T4 Ndd nucleoid disruption protein; small early phage protein acting on host chromosome organization (pqac-00000005, pqac-00000007) | Bouet et al., 1994, *Gene* | https://doi.org/10.1016/0378-1119(94)90121-X |
| Nucleoid disruption begins very early after T4 infection and requires phage gene expression | Review of primary experiments, microscopy/physiology | Onset within **2–3 min** postinfection; blocked by chloramphenicol when added at infection | *E. coli* infected with T4 or T-even phages | Places Ndd function in the **early infection stage** inside the bacterial cytoplasm/nucleoid region rather than at late morphogenesis (pqac-00000001, pqac-00000006, pqac-00000012) | Koerner & Snustad, 1979, *Microbiological Reviews* | https://doi.org/10.1128/mr.43.2.199-223.1979 |
| **ndd** is not required for basic phage viability in common laboratory strains, but can be important in specific hosts | Genetics, review | Wild-type growth largely normal in standard hosts; in strain CT447, wild-type burst size **~150–200 PFU/cell** versus **~15 PFU/cell** for **ndd** mutants | T4 infection of different *E. coli* hosts, especially CT447 | Ndd is **host-context dependent**: dispensable in some strains but important for full fitness in restrictive backgrounds (pqac-00000002, pqac-00000006, pqac-00000008) | Koerner & Snustad, 1979, *Microbiological Reviews* | https://doi.org/10.1128/mr.43.2.199-223.1979 |
| Loss of **ndd** delays shutoff of host DNA synthesis but does not strongly affect host RNA/protein shutoff | Review of primary physiological studies | Host DNA synthesis shutoff at **~4 min** with **ndd+** phage versus **~10 min** with **ndd** mutants | T4-infected *E. coli* | Functional annotation: Ndd primarily contributes to **rapid host nucleoid remodeling linked to host DNA synthesis shutoff**, not general macromolecular shutoff (pqac-00000000, pqac-00000008) | Koerner & Snustad, 1979, *Microbiological Reviews* | https://doi.org/10.1128/mr.43.2.199-223.1979 |
| Ndd-dependent nuclear disruption is not simply caused by extensive host DNA nicking or breakage | Biochemistry, review | At **5 min**, about **≤5 single-strand breaks per strand**; by **30 min**, **~15–20 breaks**; little difference attributable to nuclear disruption status; most host DNA remained **>10^8 daltons** at 5 min | Sucrose-gradient and DNA break analyses in infected *E. coli* | Supports a **structural reorganization mechanism** rather than direct nuclease activity for Ndd; no catalytic substrate specificity has been demonstrated (pqac-00000001, pqac-00000012) | Koerner & Snustad, 1979, *Microbiological Reviews* | https://doi.org/10.1128/mr.43.2.199-223.1979 |
| Wild-type infection causes progressive release of host DNA from membrane-associated fractions; this is strongly reduced in **ndd**-defective backgrounds | Biochemistry, review | Host DNA begins release at **~10 min**; by **30 min**, about **~75%** released from membrane in wild type, whereas **>80%** remains membrane-associated in endonuclease- and **ndd**-deficient infections | M-band assays in T4-infected *E. coli* | Suggests Ndd promotes **host chromosome redistribution toward/along the inner membrane** or alters DNA-membrane attachments during infection (pqac-00000002, pqac-00000009) | Koerner & Snustad, 1979, *Microbiological Reviews* | https://doi.org/10.1128/mr.43.2.199-223.1979 |
| Earlier authors proposed Ndd may act stoichiometrically as a structural bridge between host DNA and membrane components, though this remains unproven | Review, genetics/physiology interpretation | Gene-dosage observations were interpreted as indicating a **stoichiometric requirement** in CT447 | T4 infection of restrictive *E. coli* CT447 and related genetic analysis | Best current mechanistic inference from classic literature: Ndd is likely a **small structural effector of nucleoid architecture/localization**, not an enzyme with defined reaction chemistry (pqac-00000002, pqac-00000009) | Koerner & Snustad, 1979, *Microbiological Reviews* | https://doi.org/10.1128/mr.43.2.199-223.1979 |
| **ndd** mutants retain substantial phage DNA synthesis in restrictive hosts but show severe defects in productive infection | Genetics, biochemistry, EM summary | Phage DNA synthesis rate **~75% of wild type** in CT447, but burst size **<5% of wild type**; EM showed **few filled or empty heads** | T4 **ndd** mutants infecting *E. coli* CT447 T4 plq+ | Indicates Ndd affects infection efficiency beyond early nucleoid remodeling, possibly by improving intracellular organization needed for maturation in some hosts (pqac-00000000, pqac-00000008) | Koerner & Snustad, 1979, *Microbiological Reviews* | https://doi.org/10.1128/mr.43.2.199-223.1979 |
| The upstream regulatory region of **ndd** contains immediate-early T4-like promoters, consistent with very early expression | Sequence analysis | Two promoter-like elements located about **~730 bp** and **~1010 bp** upstream of the start codon | T4 genomic DNA sequence analysis | Reinforces annotation of Ndd as an **early phage protein** acting shortly after infection begins (pqac-00000004) | Bouet et al., 1994, *Gene* | https://doi.org/10.1016/0378-1119(94)90121-X |
| Ectopic Ndd expression in *E. coli* disrupts and relocalizes the nucleoid to the inner membrane | Microscopy | Figure-based cellular phenotype; no additional numeric value reported in the retrieved evidence | *E. coli* expressing bacteriophage T4 Ndd, visualized by DAPI/fluorescence microscopy | Direct localization-level evidence that Ndd acts **inside infected cells on host nucleoid architecture**, causing peripheral nucleoid redistribution (pqac-00000013, pqac-00000014) | Winkler et al., 2010, *The EMBO Journal* | https://doi.org/10.1038/emboj.2009.412 |
| Modern phage-engineering workflows explicitly target T4 genomic regions containing **ndd**, demonstrating current practical relevance | Application, genetics | Homologous-recombination edits initially at **~0.1–1%** in mixed lysates; after Cas13a enrichment, edited phage approached **nearly 100%** of survivors in reported workflows | Cas13a-assisted editing of T4/T4-like phages | Real-world implementation: **ndd-containing loci are tractable in modern phage genome engineering**, although this does not add a new mechanistic annotation for Ndd itself (pqac-00000015) | Adler et al., 2022, *Nature Microbiology* | https://doi.org/10.1038/s41564-022-01258-x |


*Table: This table summarizes experimentally supported functional-annotation facts for bacteriophage T4 Ndd (UniProt P15556), including timing, phenotypes, localization inferences, and modern applications. It is useful for tracing each annotation claim to specific evidence and quantitative observations.*