The invention provides engineered Vibrio sp. organisms that comprise a genetic modification to either or both of the lpxL and/or lpxM genes. The organisms score substantially lower in an in vitro endotoxin assay versus the unmodified or wild type organism. The organisms preserve substantially the growth rate of the corresponding unmodified organisms. The organisms can also have an exogenous nucleic acid cloned in the organism, or an exogenous nucleic acid encoding a protein, polypeptide, or peptide expressed by the organism, and optionally secreted from the organism.