uclust: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/lib/qiime/bin/uclust - from package: qiime

You may install the required package with command apt-get install {package}

Error in other languages:
uclust: bevel nie gevind nie
uclust: comandă negăsită
uclust: comando não encontrado
uclust: commande introuvable
uclust: command not found
uclust: käsku ei ole
uclust: không tìm thấy lệnh
uclust: komanda nerasta
uclust: Kommando nicht gefunden.
uclust: kommandot finns inte
uclust: komut yok
uclust: nie znaleziono polecenia
uclust: níor aimsíodh an t-ordú
uclust: no se encontró la orden
uclust: no s'ha trobat l'ordre
uclust: opdracht niet gevonden
uclust: parancs nem található
uclust: perintah tidak ditemukan
uclust: príkaz nenájdený
uclust: příkaz nenalezen
uclust: команда не найдена
uclust: командата не е открита
uclust: 命令找不到
uclust: コマンドが見つかりません