How to change the shape of reference numbers in the bibliography

I have the following document. After compiling the document, the reference number in the bibliography appears as [ 1 ]. I would like to know if it would be possible to do the following customizations without introducing any external package.

• [ 1 ] appears as [1], i.e., the reference number becomes italic.


• [ 1 ] appears as [1], i.e., the reference number becomes bold.


• [ 1 ] appears as , i.e., just the reference number (and not the brackets) becomes bigger.

Of course I can do these manually, i.e., by writing

\bibitem[\mbox{\it{1}}]{one}
\bibitem[\mbox{\bf{1}}]{one}
\bibitem[\mbox{\Large{1}}]{one}

But I would like to do them automatically, i.e., for all references.

\documentclass{article}
\begin{document}
This is a text.

\begin{thebibliography}{MM}
\bibitem{one}
\end{thebibliography}
\end{document}