Diatoms are responsible for 40% of marine primary production and nearly one-quarter of the global primary production, which involves the synthesis of organic compounds from CO2.However, some of them cause harmful algal blooms (HABs), which bring about huge effects on marine ecosystems and economics, and even poison people by producing toxins.Bacteria-algae interactions during bloom are complex and change throughout the lifetime of the bloom.Most reported algicidal bacteria have an inhibitory effect on algal growth by excreting extracellular substances, which is regarded as allelopathy.