clustalx software package provides Multiple alignment of nucleic acid and protein sequences (graphical interface), you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install clustalx
clustalx is installed in your system.
Make ensure the clustalx package were installed using the commands given below,
$ sudo dpkg-query -l | grep clustalx *
You will get with clustalx package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Science |
| Package | clustalx |
| Version | 2.1+lgpl-5 |
| Description | Multiple alignment of nucleic acid and protein sequences (graphical interface) |
| Sub Section | Science |