In order to admit a mortgage to record, it must be attested by or acknowledged before an officer as prescribed for the attestation or acknowledgment of deeds of bargain and sale; and, in the case of real property, a mortgage must also be attested or acknowledged by one additional witness. In the absence of fraud, if a mortgage is duly filed, recorded, and indexed on the appropriate county land records, such recordation shall be deemed constructive notice to subsequent bona fide purchasers.