Secretion Kills Bacteria

Biological Strategy

Burying beetles

AskNature Team

Protect From Microbes

In living systems, microbes play important roles, such as breaking down organic matter and maintaining personal and system health. But they also pose threats. Bacteria can be pathogens that cause diseases. Some bacteria create colonies called biofilms that can coat surfaces, reducing their effectiveness–for example, inhibiting a leaf’s ability to photosynthesize. Living systems must have strategies for protecting from microbes that cause disease or become so numerous that they create an imbalance in the system. At the same time, living systems must continue living in harmony with other microbes. Some living systems kill microbes. Others repel without killing to reduce the chances that microbes will adapt to the lethal strategy and become resistant to it. For example, some pea seedlings exude a chemical that inhibits biofilm buildup.

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Physically Break Down Living Materials

Living materials are those that are part of living systems (whether currently or formerly alive). For example, a fallen log, although dead, is considered a living material. Breaking down or breaking up living materials is important for living systems that feed on them, as well as in facilitating the decomposition of organic matter. Breakdown increases the material’s surface area exposed to moisture, fungi, bacteria, and other living systems, many of which use enzymes and other chemicals to further break it down. But living materials can be difficult to break down because, for their own survival, their composition must provide support and protection. Therefore, living systems require mechanical means (such as grinding, tearing, or chewing) to manipulate these materials, as well as strong materials that can overcome resistance. For example, small beetles that chew through wood have large, strong jaws that enable them to cut through this tough material.

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Insects

Class Insecta (“an insect”): Flies, ants, beetles, cockroaches, fleas, dragonflies

Insects are the most abundant arthropods—they make up 90% of the animals in the phylum. They’re found everywhere on earth except the deep ocean, and scientists estimate there are millions of insects not yet described. Most live on land, but many live in freshwater or saltwater marshes for part of their life cycles. Insects have three distinct body sections: a head, which has specialized mouthparts, a thorax, which has jointed legs, and an abdomen. They have well-developed nervous and sensory systems, and are the only invertebrate that can fly, thanks to their lightweight exoskeletons and small size.

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Glands of burying beetles produce a secretion that kills bacteria by chopping microbial cell walls.

“Burying beetles lay their eggs on the carcasses of small animals, such as birds and rodents…But a buried carcass is not going to stay fresh for very long, and the bacterial communities that colonise it are likely to threaten the beetle’s developing larvae…So burying beetles use secretions from their anal glands to coat the fur or feathers with substances that guarantee the carcass stays germ-free and fresh for longer…The researchers [from the University of Manchester] extracted secretions from the anal glands of a species of burying beetle called Nicrophorus vespilloides, and showed that when this substance was added to bacterial cells, they were destroyed…[They suspected] they were dealing with a[n] enzyme that ‘chops up microbial cell walls’, investigated and confirmed that the secretions were rich in lysozymes.These are anti-microbial enzymes, and a common component of animals’ immune systems.” (Carpenter 2011:1)

“Offspring of many animals develop in environments in which they are exposed to high densities ofpotentially harmful bacteria. For example, larvae of the carrion beetle Nicrophorus vespilloides face significant challenges from the bacteria they encounter during their development on decomposing vertebrate carcasses. We tested the idea that larvae secrete antimicrobial compounds during development to defend themselves against microbial exposure. We first showed that larval secretion of active antimicrobials peaked during the early stages of development. As has been found previously for parental secretions, larval secretions were active against Gram-positive but not Gram-negative bacteria, indicating that they might be based on lysozyme-like compounds. Finally, consistent with this antibacterial activity, we showed that larval survival declined significantly when challenged with lysozyme-resistant Staphylococcus aureus but not when challenged with a lysozyme-susceptible strain of the same species. These results demonstrate that Nicrophorus larvae are not simply passive recipients of social immunity derivedfrom their parents, but that they are active participants in its production.” (Arce et al. 2013:1)