The zigzag model of plant-microbe interactions: is it time to move on?

Microbe-plant interactions represent a dynamic spectrum of associations shaped by intricate chemical signaling. These interactions can be neutral, beneficial, or detrimental, and profoundly influence plant physiology, growth, and ecosystem function. The plant microbiome, comprising bacteria, fungi, archaea, protists, and viruses, plays a pivotal role in mediating these effects through surface colonization, internal colonization, or systemic symbiosis.Mutualistic associations, particularly with...

Plants have the impressive ability to create their own food through photosynthesis. However, plants often require assistance from organisms in the soil to acquire the nutrients they need to function correctly. Both bacteria and fungi have evolved symbiotic relationships with plants that help the species to thrive in a wide variety of environments.

Microbial cooperation involves beneficial interactions in which different species work together for individual or mutual advantage. These interactions can profoundly influence ecological dynamics and evolutionary processes, and they are essential to many pathogenic and symbiotic relationships.Nematode–Bacteria CooperationA striking example is the relationship between the Gram-negative bacterium Xenorhabdus nematophila and the parasitic nematode Steinernema carpocapsae. Juvenile nematodes...

Mutualism is a symbiotic interaction in which all participating organisms benefit. These relationships can be obligate or facultative and are fundamental to ecosystem functions across diverse biological systems.Plant–Fungi MutualismOne well-known example is the association between plant roots and mycorrhizal fungi, such as Rhizophagus species. The fungal hyphae penetrate the root hairs and the epidermis, forming an extensive hyphal network that establishes a symbiotic association. Through...

Parasitism is a form of microbial interaction in which parasitic microbes exploit a host organism for nutrients and shelter, often at the host's expense. Unlike mutualistic relationships, where both organisms benefit, parasitism benefits only the parasite and harms the host.Classification of ParasitesMicrobial parasites are broadly classified based on their location relative to the host.Ectoparasites remain on the host’s surface, such as the skin or outer tissues, drawing nutrients...

Plants often form mutualistic relationships with soil-dwelling fungi or bacteria to enhance their roots’ nutrient uptake ability. Root-colonizing fungi (e.g., mycorrhizae) increase a plant’s root surface area, which promotes nutrient absorption. While root-colonizing, nitrogen-fixing bacteria (e.g., rhizobia) convert atmospheric nitrogen (N2) into ammonia (NH3), making nitrogen available to plants for various biological functions. For example, nitrogen is essential for the...