Burkholderia sensu lato is a large and complex group, containing pathogenic, phytopathogenic, symbiotic and non-symbiotic strains from a very wide range of environmental (soil, water, plants, fungi) and clinical (animal, human) habitats. Its taxonomy has been evaluated several times through the analysis of 16S rRNA sequences, concantenated 4–7 housekeeping gene sequences, and lately by genome sequences. Currently, the division of this group into Burkholderia, Caballeronia, Paraburkholderia, and Robbsia is strongly supported by genome analysis. These new genera broadly correspond to the various habitats/lifestyles of Burkholderia s.l., e.g., all the plant beneficial and environmental (PBE) strains are included in Paraburkholderia (which also includes all the N2-fixing legume symbionts) and Caballeronia, while most of the human and animal pathogens are retained in Burkholderia sensu stricto. However, none of these genera can accommodate two important groups of species. One of these includes the closely related Paraburkholderia rhizoxinica and Paraburkholderia endofungorum, which are both symbionts of the fungal phytopathogen Rhizopus microsporus. The second group comprises the Mimosa-nodulating bacterium Paraburkholderia symbiotica, the phytopathogen Paraburkholderia caryophylli, and the soil bacteria Burkholderia dabaoshanensis and Paraburkholderia soli. In order to clarify their positions within Burkholderia sensu lato, a phylogenomic approach based on a maximum likelihood analysis of conserved genes from more than 100 Burkholderia sensu lato species was carried out. Additionally, the average nucleotide identity (ANI) and amino acid identity (AAI) were calculated. The data strongly supported the existence of two distinct and unique clades, which in fact sustain the description of two novel genera Mycetohabitans gen. nov. and Trinickia gen. nov. The newly proposed combinations are Mycetohabitans endofungorum comb. nov., Mycetohabitans rhizoxinica comb. nov., Trinickia caryophylli comb. nov., Trinickia dabaoshanensis comb. nov., Trinickia soli comb. nov., and Trinickia symbiotica comb. nov. Given that the division between the genera that comprise Burkholderia s.l. in terms of their lifestyles is often complex, differential characteristics of the genomes of these new combinations were investigated. In addition, two important lifestyle-determining traits—diazotrophy and/or symbiotic nodulation, and pathogenesis—were analyzed in depth i.e., the phylogenetic positions of nitrogen fixation and nodulation genes in Trinickia via-à-vis other Burkholderiaceae were determined, and the possibility of pathogenesis in Mycetohabitans and Trinickia was tested by performing infection experiments on plants and the nematode Caenorhabditis elegans. It is concluded that (1) T. symbiotica nif and nod genes fit within the wider Mimosa-nodulating Burkholderiaceae but appear in separate clades and that T. caryophylli nif genes are basal to the free-living Burkholderia s.l. strains, while with regard to pathogenesis (2) none of the Mycetoh...

Fusarium is a complex genus of ascomycete fungi that consists of plant pathogens of agricultural relevance. Controlling Fusarium infection in crops that leads to substantial yield losses is challenging. These economic losses along with environmental and human health concerns over the usage of chemicals in attaining disease control are shifting focus toward the use of biocontrol agents for effective control of phytopathogenic Fusarium spp. In the present study, an analysis of the plant-growth promoting (PGP) and biocontrol attributes of four bacilli (Bacillus simplex 30N-5, B. simplex 11, B. simplex 237, and B. subtilis 30VD-1) has been conducted. The production of cellulase, xylanase, pectinase, and chitinase in functional assays was studied, followed by in silico gene analysis of the PGP-related and biocontrol-associated genes. Of all the bacilli included in this study, B. subtilis 30VD-1 (30VD-1) demonstrated the most effective antagonism against Fusarium spp. under in vitro conditions. Additionally, 100 μg/ml of the crude 1-butanol extract of 30VD-1’s cell-free culture filtrate caused about 40% inhibition in radial growth of Fusarium spp. Pea seed bacterization with 30VD-1 led to considerable reduction in wilt severity in plants with about 35% increase in dry plant biomass over uninoculated plants growing in Fusarium-infested soil. Phase contrast microscopy demonstrated distortions and abnormal swellings in F. oxysporum hyphae on co-culturing with 30VD-1. The results suggest a multivariate mode of antagonism of 30VD-1 against phytopathogenic Fusarium spp., by producing chitinase, volatiles, and other antifungal molecules, the characterization of which is underway.

Cyclooxygenase-2 (Cox-2) is an inducible enzyme involved in the conversion of arachidonic acid to prostaglandin and other eicosanoids. Molecular pathology studies have revealed that Cox-2 is over-expressed in cancer and stroma cells during tumor progression, and anti-cancer chemo-radiotherapies induce expression of Cox-2 in cancer cells. Elevated tumor Cox-2 is associated with increased angiogenesis, tumor invasion and promotion of tumor cell resistance to apoptosis. Several experimental and clinical studies have established potent anti-cancer activity of NSAID (Non-steroidal anti-inflammatory drugs) and other Cox-2 inhibitors such as celecoxib. Much attention is being focused on Cox-2 inhibitors as beneficial target for cancer chemotherapy. The mode of action of Cox-2 and its inhibitors remains unclear. Further clinical application needs to be investigated for comprehending Cox-2 biological functions and establishing it as an effective target in cancer therapy.

Graphical abstract

Despite efforts to control toxigenic Fusarium species, wilt and head-blight infections are destructive and economically damaging diseases that have global effects. The utilization of biological control agents in disease management programs has provided an effective, safe, and sustainable means to control Fusarium-induced plant diseases. Among the most widely used microbes for biocontrol agents are members of the genus Bacillus. These species influence plant and fungal pathogen interactions by a number of mechanisms such as competing for essential nutrients, antagonizing pathogens by producing fungitoxic metabolites, or inducing systemic resistance in plants. The multivariate interactions among plant-biocontrol agent-pathogen are the subject of this study, in which we survey the advances made regarding the research on the Bacillus-Fusarium interaction and focus on the principles and mechanisms of action among plant-growth promoting Bacillus species. In particular, we highlight their use in limiting and controlling Fusarium spread and infestations of economically important crops. This knowledge will be useful to define strategies for exploiting this group of beneficial bacteria for use as inoculants by themselves or in combination with other microbes for enhanced crop protection.