Taking Root: Enduring Effect of Rhizosphere Bacterial Colonization in Mangroves

Abstract

BackgroundMangrove forests are of global ecological and economic importance, but are also one of the world's most threatened ecosystems. Here we present a case study examining the influence of the rhizosphere on the structural composition and diversity of mangrove bacterial communities and the implications for mangrove reforestation approaches using nursery-raised plants.Methodology/Principal FindingsA barcoded pyrosequencing approach was used to assess bacterial diversity in the rhizosphere of plants in a nursery setting, nursery-raised transplants and native (non-transplanted) plants in the same mangrove habitat. In addition to this, we also assessed bacterial composition in the bulk sediment in order to ascertain if the roots of mangrove plants affect sediment bacterial composition. We found that mangrove roots appear to influence bacterial abundance and composition in the rhizosphere. Due to the sheer abundance of roots in mangrove habitat, such an effect can have an important impact on the maintenance of bacterial guilds involved in nutrient cycling and other key ecosystem functions. Surprisingly, we also noted a marked impact of initial nursery conditions on the rhizosphere bacterial composition of replanted mangrove trees. This result is intriguing because mangroves are periodically inundated with seawater and represent a highly dynamic environment compared to the more controlled nursery environment.Conclusions/SignificanceIn as far as microbial diversity and composition influences plant growth and health, this study indicates that nursery conditions and early microbial colonization patterns of the replants are key factors that should be considered during reforestation projects. In addition to this, our results provide information on the role of the mangrove rhizosphere as a habitat for bacteria from estuarine sediments.

Characteristics of meiofauna in extreme marine ecosystems: a review

“…These conditions result from complex sedimentary processes that are driven by a large number of interacting physical and biological factors, such as the geological and physiographical characteristics of the area, climatic conditions and the nature of mangrove vegetation (Middelburg et al 1996;Marchand et al 2004). On a small scale, the mangrove root habitat is exposed to extreme changes on a daily basis due to tidal cycles (Gomes et al 2010). Mangrove are able to grow in reduced sediments due to the capacity of the plant to maintain aerobic metabolism in its roots and mechanisms for detoxifying or adapting to soil phytotoxins (Matthijs et al 1999).…”

Denaturing Gradient Gel Electrophoresis and Barcoded Pyrosequencing Reveal Unprecedented Archaeal Diversity in Mangrove Sediment and Rhizosphere Samples

“…These forests are ecologically and economically important, since they limit erosion in coastal areas, reduce the impact of waves and tsunamis, and are used by several aquatic animals during some part of their life cycle (1,16,27). Mangroves also harbor microorganisms that are important in nutrient cycling (31,40). Many species of terrestrial plants influence microbial communities inhabiting their roots; this phenomenon is known as the rhizosphere effect (33,39).…”

Sulphur oxidising bacteria in mangrove ecosystem: A review

“…The potential effect of mangrove roots on sediment proteobacterial populations may influence several environmentally relevant processes in mangrove ecosystems. Gomes et al (2010) observed that Chromatiales was the second most abundant proteobacterial order and was detected in all samples from an urban mangrove habitat located in Guanabara Bay, Rio de Janeiro, Brazil. This order is represented by anaerobic or microaerophilic microorganisms specialized in sulphur-an oxygenic photosynthesis and are able to oxidize hydrogen sulphide (H 2 S) to elemental sulphur (Imhoff, 2006).…”

“…This genus is known to be an important player in the process of sulphideoxidation and denitrification in marine environments (Sievert et al, 2008). The genus Listonella includes diazotrophic members with some representative previously detected from mangrove rhizosphere (Gomes et al, 2010). Hart (1958;1959;1962) demonstrated that mangrove peat contains large amounts of sulphides and polysulphides.…”