Demo

Create some fake data:

d <- data.frame(
  organism=c("Grasshopper", "Bumblebee", "MycoTB"), 
  protein=c("Jumpylegs", "venom-1", "rpoB"), 
  accession=c("Gr1,Gr2,Gr3", "Bbv4,Bbv5,Bbv6", "Mtb1,Mtb2,Mtb3,Mtb4,Mtb5")
)

This is what your data looks like:

d

##      organism   protein                accession
## 1 Grasshopper Jumpylegs              Gr1,Gr2,Gr3
## 2   Bumblebee   venom-1           Bbv4,Bbv5,Bbv6
## 3      MycoTB      rpoB Mtb1,Mtb2,Mtb3,Mtb4,Mtb5

One command to “separate” rows by the comma in the accession column:

library(tidyr)
separate_rows(d, accession, sep=",")

##       organism   protein accession
## 1  Grasshopper Jumpylegs       Gr1
## 2  Grasshopper Jumpylegs       Gr2
## 3  Grasshopper Jumpylegs       Gr3
## 4    Bumblebee   venom-1      Bbv4
## 5    Bumblebee   venom-1      Bbv5
## 6    Bumblebee   venom-1      Bbv6
## 7       MycoTB      rpoB      Mtb1
## 8       MycoTB      rpoB      Mtb2
## 9       MycoTB      rpoB      Mtb3
## 10      MycoTB      rpoB      Mtb4
## 11      MycoTB      rpoB      Mtb5