Binary tree store in php mysql?

I am working on a MLM project in which i have more than 30,000 members followed by the root member,i have to store member automatically in binary tree form like

1 is root
2 is child of 1
3 is child of 1

Then 4 is child of 2
5 is child of 2

and so on ......


I have calculate each members left count and right count in downline, calculation takes 30minutes for 10,000 members, now i have more than 30,000 members it takes more time.... How to avoid this.....

Here is my table structure

ID Root MemberID lft rgt
1 0 1000 8 8
2 1000 1001 0 7
3 1001 1002 1 6
4 1002 1003 2 5


can any body help me ...