My new landlord just notified me that they have taken over the building

If you have a current lease in place, they are required to keep it till it ends. When the lease ends, they can provide you a notice to terminate the lease.

Generally, Mr. Iloulian is correct - where there has been a sale by your old landlord to your new landlord of the property, the new landlord is bound to the terms of the contract (i.e., the commercial lease). However, there is an exception. If the sale of the building you operate your business from was sold/transferred as a result of a foreclosure sale, your rights to stay are determined by: (1) when your lease was signed vs. when the mortgage that has been foreclosed was signed; and (2) whether or not the terms of your commercial lease contain a subordination/attornment clause. If your lease was signed before the previous landlord signed the mortgage, then your lease is superior to the mortgage (until the end of the term of the lease). However, if your lease contained a subordination clause that makes your lease subordinate to any subsequent mortgages on the property, then the mortgage is superior to your lease. I highly recommend two actions: (1) review the terms of your commercial lease, as this often times answers more questions than not; and (2) determine whether this property was sold as a result of a foreclosure sale. If so, you may wish to consult with an attorney in the Fremont or Alameda County who can provide you with more detailed guidance based on the terms of your lease and the facts involved.