how to write a file so that it does not have commas and remains in same format in R

Question

I am reading file in R:

data <- read.delim ("file.fas", header=TRUE, sep="\t" )

However, after I have done some manipulations to the data, the output format is not same. It now contains commas "," like this all over.

write.table(x= data, file = "file_1.fas")

How can I avoid this? Maybe I should use some different function to write a file?