Interactions among endophytic bacteria and fungi: Effects and potentials

Abstract

Plants benefit extensively by harbouring endophytic microbes. They promote plant growth and confer enhanced resistance to various pathogens. However, the way the interactions among endophytes influence the plant productivity has not been explained. Present study experimentally showed that endophytes isolated from rice (Oryza sativa) used as the test plant produced two types of interactions; biofilms (bacteria attached to mycelia) and mixed cultures with no such attachments. Acidity, as measured by pH in cultures with biofilms was higher than that of fungi alone, bacteria alone or the mixed cultures. Production of indoleacetic acid like substances (IAAS) of biofilms was higher than that of mixed cultures, fungi or bacteria. Bacteria and fungi produced higher quantities of IAAS than mixed cultures. In mixed cultures, the potential of IAAS production of resident microbes was reduced considerably. There was a negative relationship between IAAS and pH of the biofilms, indicating that IAAS was the main contributor to the acidity. However, such a relationship was not observed in mixed cultures. Microbial acid production is important for suppressing plant pathogens. Thus the biofilm formation in endophytic environment seems to be very important for healthy and improved plant growth. However, it is unlikely that an interaction among endophytes takes place naturally in the endophytic environment, due to physical barriers of plant tissues. Further, critical cell density dependant quorum sensing that leads to biofilm formation may not occur in the endophytic environment as there is a limited space. As such in vitro production and application of beneficial biofilmed inocula of endophytes are important for improved plant production in any agro-ecosystem. The conventional practice of plant inoculation with monocultures or mixed cultures of effective microbes may not give the highest microbial effect, which may only be achieved by biofilm formation.

Determination of desirable properties of bacteria, fungi and their biofilm associated with rubber rhizosphere

“…Moreover, the IAA production of biofilm was ranging from 3-7ppm and higher than their mono cultures. There is evidence that the capacity of producing IAA was higher with biofilm compared to their bacterial only cultures (Bandara et al, 2006;Seneviratne et al, 2009). …”

Biosynthesis of silver nanoparticles by endophytic fungi: Its mechanism, characterization techniques and antimicrobial potential

“…They are found to inhabit almost all classes of vascular plants and grasses examined to date (Zhang et al, 2006). Besides fungi, different groups of organisms such as bacteria, actinomycetes and mycoplasma are reported as endophytes of plants (Bandara et al, 2006). Their existence has been known for over one hundred years.…”

Comments on bacterial and fungal interactions in medicine, agriculture and the environment

“…Thus, the biofilm production in endophytic ambient ostensibly relates to healthy and improved plant growth. It may not be possible that endophyte interactions occur in nature within the endophytic ambience as a result of plant tissue physical barriers (Bandara et al, 2006). Critical cell density dependent quorum sensing that culminates in biofilm production is not liable to manifest in an endophytic ambient due to restricted arena.…”

“…Inevitably, in vitro formation and beneficial biofilm inocula endophyte application are performed for enhanced agro-ecosystem plant production. It is suggested that the traditional plant inoculation procedure with monocultures or mixed cultures of potent microbes ay not result in optimal microbial impact that may be achievable via biofilm production (Bandara et al, 2006).…”