r - How to italicize part (one or two words) of an axis title

Question

Is there any way to change the style of part of an axis title while keep the rest part unchanged? In my case, How could I italicize
"bacteria X" in the y-axis title? To my knowledge, the command theme(axis.title.y=element_text(face="italic")) can only change the whole y-aixs title, is it?

ggplot(fig1,aes(x=cf,y=Freq,fill=Var1)) +
geom_bar(stat="identity") +
labs(x="Groups",y="No. of bacteria X isolates with corresponding types",fill="Var1") +
theme(axis.title.y=element_text(face="italic"))

Answer 1

You could make an expression like this:

my_y_title <- expression(paste("No. of ", italic("bacteria X"), " isolates with corresponding types"))
.... + labs(y=my_y_title)