fmicb-08-00172 February 8, 2017 Time: 14:51 # 1 ORIGINAL RESEARCH published: 10 February 2017 doi: 10.3389/fmicb.2017.00172 Plant Growth Promoting Bacteria Associated with Langsdorffia hypogaea-Rhizosphere-Host Biological Interface: A Neglected Model of Bacterial Prospection Érica B. Felestrino1,2, Iara F. Santiago3, Luana da Silva Freitas4, Luiz H. Rosa3, Sérvio P. Ribeiro4 and Leandro M. Moreira1,2* 1 Núcleo de Pesquisas em Ciências Biológicas, Universidade Federal de Ouro Preto, Ouro Preto, Brazil, 2 Laboratório de Genômica e Interação Microrganismos-Ambiente, Departamento de Ciências Biológicas, Instituto de Ciências Exatas e Biológicas, Universidade Federal de Ouro Preto, Campus Morro do Cruzeiro, Ouro Preto, Brazil, 3 Laboratório de Ecologia e Biotecnologia de Leveduras, Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil, 4 Programa de Pós-Graduação em Biomas Tropicais, Departamento de Biodiversidade, Evolução e Meio Ambiente, Instituto de Ciências Exatas e Biológicas, Universidade Federal de Ouro Preto, Ouro Preto, Brazil Soil is a habitat where plant roots and microorganisms interact. In the region Edited by: Gero Benckiser, of the Brazilian Iron Quadrangle (IQ), studies involving the interaction between University of Giessen, Germany microbiota and plants have been neglected. Even more neglected are the studies Reviewed by: involving the holoparasite plant Langsdorffia hypogaea Mart. (Balanophoraceae). The Daolong Dou, geomorphological peculiarities of IQ soil, rich in iron ore, as well as the model of Nanjing Agricultural University, China Dananjeyan Balachandar, interaction between L. hypogaea, its hosts and the soil provide a unique niche that Tamil Nadu Agricultural University, acts as selective pressure to the evolution of plant growth-promoting bacteria (PGPB). India The aim of this study was to prospect the bacterial microbiota of holoparasitic plant *Correspondence: Leandro M. Moreira L. hypogaea, its plant host and corresponding rhizosphere of IQ soil, and to analyze [email protected] the potential of these isolates as PGPB. We obtained samples of 11 individuals of L. hypogaea containing fragments of host and rhizosphere remnants, resulting in 81 Specialty section: This article was submitted to isolates associated with Firmicutes and Proteobacteria phyla. The ability to produce Plant Microbe Interactions, siderophores, hydrocyanic acid (HCN), indole-3-acetic acid (IAA), nitrogen (N2) fixation, a section of the journal hydrolytic enzymes secretion and inhibition of enteropathogens, and phytopathogens Frontiers in Microbiology were evaluated. Of the total isolates, 62, 86, and 93% produced, respectively, Received: 29 July 2016 Accepted: 24 January 2017 siderophores, IAA, and were able to fix N2. In addition, 27 and 20% of isolates inhibited Published: 10 February 2017 the growth of enteropathogens and phytopathogens, respectively, and 58% were able Citation: to produce at least one hydrolytic activity investigated. The high number of isolates Felestrino ÉB, Santiago IF, Freitas LS, Rosa LH, Ribeiro SP and that produce siderophores and indole-3-acetic acid suggests that this microbiota may Moreira LM (2017) Plant Growth be important for adaptation of plants to IQ. The results demonstrate for the first time Promoting Bacteria Associated with the biological importance of Brazilian IQ species as reservoirs of specific microbiotas Langsdorffia hypogaea-Rhizosphere-Host that might be used as PGPB on agricultural land or antropized soils that needs to be Biological Interface: A Neglected reforested. Model of Bacterial Prospection. Front. Microbiol. 8:172. Keywords: Langsdorffia hypongaea, bioprospecting, biotechnological potential, plant growth-promoting doi: 10.3389/fmicb.2017.00172 bacteria, Brazilian Iron Quadrangle, IAA and siderophores Frontiers in Microbiology| www.frontiersin.org 1 February 2017| Volume 8| Article 172 fmicb-08-00172 February 8, 2017 Time: 14:51 # 2 Felestrino et al. PGPB Associated with Holoparasitic Plant Interfaces INTRODUCTION of this soil rich in iron ore as well as the model of interaction with plants provide a unique niche that acts as a selective pressure to Throughout evolution, plants have developed adaptive the evolution of PGPR. Furthermore, these peculiarities make mechanisms related to interactions with microorganisms (Zilber- this environment a potential hostspot of microbial diversity. Rosenberg and Rosenberg, 2008). Accordingly, plants comprise a Belonging to a geologically very old craton that covers about complex host system, made up of different microhabitats that can 7200 km2, the IQ extends between southeast of Ouro Preto and be simultaneously colonized by a great diversity of endophytic northeast of Belo Horizonte, continuing to the south of Serra do and epiphytic microorganisms (Lodewyckx et al., 2002). This Espinhaço. In this region, there are rocky outcrops that have a microbial community is essential for the development of plants naturally high contamination of soil with heavy metals, which since it facilitates the absortion of nutrients and at the same time makes the environment very adverse for many plant species. provides protection against phytopathogens (Fungi, oomycetes, Despite this adverse condition, the IQ presents a great floristic bacteria, viroses, protozoa, and nematodes) and herbivores diversity with high levels of endemism (Jacobi and do Carmo, (Lynch and Whipps, 1990). 2008). Due to its association with an extensive deposit of iron The rhizosphere or portion of soil that has close contact ore, and since it is one of the least studied ecosystems in Brazil, with the plant roots represents a highly dynamic environment IQ has a seriously threatened biodiversity due to the intense that enables the interaction of roots with beneficial and mining activity associated with its iron outcrops. pathogenic microorganisms, invertebrates and even root systems Among the plant species threatened by this anthropic activity of other plants (Bais et al., 2006; Raaijmakers et al., 2009). The in IQ, there have been few studies particularly on holoparasitic communication between the plant roots and organisms present plants, as in the case of Langsdorffia hypogaea MART, the in the rhizosphere is based on the production and secretion of model of this study, being Asteraceae (Guatteria genus), Fabaceae chemicals that can cause different responses depending on the (Dalbergia genus), Melastomataceae (Miconia genus), and sensitivity or responsiveness of microorganisms present in this Myrsinaceae (Myrsine genus) the most representative families highly dynamic environment (Jones et al., 1994; Bertin et al., of potential host plants from L. hypogaea (Vale, 2013). There 2003; Badri et al., 2009). are approximately 4200 species of parasitic plants distributed Some microorganisms present in this plant rhizosphere- in 18 families and 274 genera (Nickrent, 2002). Langsdorffia interface have the ability to solubilize mineral phosphates, among hypogaea is one of the 44 species of plants described belonging other soil nutrients (Rodriguez and Fraga, 1999). Many of to the family Balanophoraceae, which includes herbaceous them synthesize, provide or increase the production of plant angiosperms, achlorophyllous plants and holoparasites of roots hormones such as indole-3-acetic acid (IAA), gibberellic acid, of trees, shrubs, and even herbaceous plants (Hsiao et al., 1995). cytokines and ethylene (Costacurta and Vanderleyden, 1995); In Brazil, this holoparasite is found in the Amazon, Caatinga, promote associative nitrogen fixation (Richardson et al., 2009); Cerrado, and Atlantic Forest (Cardoso, 2014), and although it and produce siderophores (Kloepper et al., 1980), hydrolytic is not threatened by extinction, due to its wide distribution, it enzymes such as glucanases, chitinases, proteases, cellulases, and is considered at risk because of substantial habitat loss, due to amylases (Bashan and de-Bashan, 2005), hydrocyanic acid (HCN) global warming (Miles et al., 2004) and human use for obtaining (Voisard et al., 1989), and even antimicrobial agents (Compant wax (Pott et al., 2004). In some places, however, it is considered et al., 2005). All these features allow classify them as plant “Rare,” and it is on the list of threatened flora of the state growth-promoting bacteria (PGPB) (Bashan and Holguin, 1998). of Paraná, Brazil (Sema/Gtz, 1995). In fact, a series of local Accordingly, plant growth is favored by the influence of the direct compromising extinctions can be disrupting the gene flow of this or indirect action of these microorganisms, which features them species so vagile in its biology of dispersion, and historical events as important biotool of agronomic and environmental interest may no longer correspond to the effective state of extinction (Mirza et al., 2001; Ramamoorthy et al., 2001; Vessey, 2003). threat. Morphologically, L. hypogaea has two regions that are well Besides this potential (Moore et al., 2003), these microorganisms distinguishable anatomically, i.e., a basal vegetative body and an are commercially important when capable of producing enzymes apical reproductive region. The vegetative body or rhizome is with different applicabilities in specific sectors. In the same way, irregularly cylindrical, elongate and epigeal, with tomentose and secondary metabolites produced by these microorganisms have fleshy appearance (Hsiao et al., 1995). The reproductive region been used in medicine, when they have antibiotic, antitumor,