Marlin and Dory meet an Anglerfish Luminescent Bacteria: the Ocean’s Night-lightsAuthor: Amy Huttlinger9 December 2010

What makes creatures of the deep glow in the darkness of the deep depths of the oceans? Special species of bacteria have evolved to emit light in the darkness and assist larger marine animals in finding food and mates. A unique mutualistic relationship exists between the bacteria and the sea creature; the small bacteria provide a light to better navigate the dark ocean floor and in turn receive vital nutrients as a thank you from the fish.

I chose this topic because I thought it was interesting that there are “glow-in-the-dark” bacteria in the ocean. There are lots of species of microbes living in the ocean, and many of them are crucial to the survival of many other ocean-dwelling species. Among these are the bacteria that live far below the ocean’s surface, where almost no light reaches. It is at this depth that some bacterial species produce light and live within a fish or other species.


Bacteria that are able to emit light in the deepest and darkest depths of the ocean are able to do so by the enzyme luciferase. It “picks up electrons from flavoproteins in the electron transport chain and then emits some of the electron’s energy as a photon of light” (Tortora 2010). The energy from this reaction is released as light, creating the visible glow when a bacterium in within a colony of its own.

During the 1870s, luminous bacteria were grown in culture, and today “the present tally of culturable marine species is about 10, three of them assigned to the genus Photobacterium, five to Vibrio and two to Shewanella” (Herring 2002). Today scientists have found it difficult to culture some bacterial species because the environment they require is very specific, and most often only found in the light organs of the fish they inhabit. Some, however, are able to be cultured, such as Photobacterium phosphoreum and Vibrio fischeri. P. phosphoreum “grows at lower temperatures than other species and is more abundant in northern waters, in winter and in deep water” (Herring). This condition makes the deep water that the angler fish inhabits suitable for the survival of this species. Although the bacteria of the angler fish have not been cultured in the laboratory, P. phosphoreum is probably in symbiosis with the fish because it is one of the few bacteria able to survive at that depth and temperature. The location of these species depends on the conditions in which they can survive. Some inhabit the oceans, while others live in freshwater streams.

Most of these luminescent microbes benefit by symbiosis: living inside a host receiving nutrients from the host while helping the host organism find its food or attracting a mate. Bacteria receive glucose nutrients from the fish, and in turn, the fish can utilize and prevent the accumulation of pyruvic acid from the bacteria. One such example of a symbiotic relationship with luminescent bacteria is the deep sea angler fish. This fish is located in the dark depths of the oceans. The female angler fish is larger than the male, with her body ranging in the size of a teacup to about two feet wide. She has large teeth and an expandable stomach, allowing her to swallow prey twice her size. One other feature is an appendage called a lure that extends in front of her face like a fishing pole. A colony of luminescent bacteria lives in the tip of this lure and shine together through quorum sensing.
The bacteria benefit from the angler fish through nutrients supplied by the bloodstream to the lure. When the fish does not want to use the light, it simply cuts off the bloodstream to the lure, and the bacteria “turn off” their light from the lack of nutrients.

Literature Cited
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