Intertidal biofilm
[1] A matrix of extracellular polymeric substances (EPS) within the biofilm forms sticky coatings on individual sediment particles and detrital surfaces.
[2] This feature protects bacteria against environmental stresses like temperature and pH fluctuations, UV exposure, changes in salinity, depletion of nutrients, antimicrobial agents, desiccation, and predation.
[7] A study of Pseudomonas aeruginosa mutants showed that twitching motility by type IV pili contributes to the organism’s ability to aggregate on substrates.
[9] In this stage, EPS prevent bacterial cells from moving, keeping them in long-term close contact and allowing interactions such as cell-to-cell communication and horizontal gene transfer to occur.
In this stage, EPS play a critical role in protecting the biofilm from environmental fluctuations such as oxidative damage, antimicrobials, and host immune system response.
[6] With the increase in cells, the biofilm matures and develops into a “tower” or “mushroom” like structure with a complex architecture of fluid-filled channels and pores.
[14] Diatoms are a major component of intertidal biofilms,[15] and they excrete EPS that support many functions, such as desiccation resistance, motility, and metabolite exchange.
[2] QS, alongside other methods of cell signaling regulation, is important for intertidal biofilms, as it allows them to survive in fluctuating environments and varying conditions.
[33] High levels of ROS induce photoinhibition, inactivating the photosystem II protein D1 and negatively affecting primary productivity.
[34] In these conditions, estuarine diatoms improve the efficiency of the xanthophyll cycle,[35] limiting the amount of photodamage and providing the biofilm with a photo-protective mechanism.
Motile diatoms migrate downwards when exposed to extreme light and temperature conditions,[44] as this allows them to be present in a moist microenvironment and mitigate the effects on photosynthetic activity.
[45] These processes are also important in biogeochemical cycles for nutrients and heavy metals due to the adsorption ability and transport function of particles in flocs.
Biofilms in the Douro River estuary were observed to engage actively in biogeochemical processes, showing considerable net primary production that greatly exceeded respiration rates.
Despite their limited spatial coverage, rocky biofilms account for a significant portion of the nitrate and silicate uptake compared to adjacent sandy and muddy sediments within the estuary.
[46] The attachment and growth of marine organisms on submerged artificial structures, such as ship hulls and aquaculture infrastructures, can cause ecological and economic issues.
[4] Biofouling on ships, both as hull fouling and through solid ballast (sand, rocks, and soil), is a major pathway for the arrival of NIS into new regions.
The microorganisms' small size, which prevents complete removal by trampling, and the biofilms' capacity for rapid recovery may contribute to their high resilience to physical disturbance.
