Hydrogel capsules as new approach for increasing drying survival of plant biostimulant gram-negative consortium.

Several plant growth-promoting bacteria (PGPB) are gram-negative, and their cell viability is affected during the bio-inoculant production. Hence, formulation-drying processes provide challenges that limit the adoption of these beneficial microorganisms in sustainable agricultural production. Among delivery system strategies for gram-negative PGPB, the encapsulating cells in biopolymeric materials are emerging as a promising alternative. This research aims to evaluate the effect of additives and crosslinking agents on the survival of the consortium of Herbaspirillum frisingense AP21, Azospirillum brasilense D7, and Rhizobium leguminosarum T88 in hydrogel capsules. Three crosslinkers and diverse potential drying protectors were tested. Calcium gluconate provides notable consortium survival advantages regarding colony-forming units (CFUs) (losses of up to 4 log CFU) compared to calcium lactate and calcium chloride (up to 6 log CFU). Additives such as skimmed milk, whey protein, and Gelita® EC improve the recovery of viable cells after the drying process, demonstrating an increase in cell survival of the three bacteria by up to 4 log CFU. The combination of these substances into a capsule prototype extends the storage stability of bacterial consortium up to 3 months at 18 ± 2 °C. This study expands the knowledge for formulating gram-negative PGPB consortium, regarding the crosslinker and drying protector relationship on encapsulation processes with drying survival and further storage stability performance. KEY POINTS: • Hydrogel immobilization formulation approach for PGPB consortium • Enhancing drying survival of gram-negative PGPB consortium • Increasing storage stability of PGPB consortium at 18 °C.

Does Organomineral Fertilizer Combined with Phosphate-Solubilizing Bacteria in Sugarcane Modulate Soil Microbial Community and Functions?

Soil bacterial and fungal communities are suitable soil ecosystem health indicators due to their sensitivity to management practices and their role in soil ecosystem processes. Here, information on composition and functions of bacterial and fungal communities were evaluated at two phenological stages of sugarcane (six and twelve months, equivalent to the most intensive vegetative stage and to final maturation, respectively) when organomineral fertilizer, combined with phosphate-solubilizing bacteria (PSB), was added into the soil. Organic compost enriched with apatite (C + A) or phosphorite (C + P) and compost without phosphate enrichment (C) were used in the presence or absence of PSB. In addition, we used a control fertilized with soluble triple superphosphate. The differences were more related to the sampling period than to the type of organomineral fertilizer, being observed higher available phosphorus at six months than at twelve months. Only in the C treatment we observed the presence of Bacillaceae and Planococcaceae, while Pseudomonadaceae were only prevalent in inoculated C + A. As for fungi, the genera Chaetomium and Achroiostachys were only present in inoculated C + P, while the genus Naganishia was most evident in inoculated C + A and in uninoculated C + P. Soliccocozyma represented 75% of the total fungal abundance in uninoculated C while in inoculated C, it represented 45%. The bacterial community was more related to the degradation of easily decomposable organic compounds, while the fungal community was more related to degradation of complex organic compounds. Although the microbial community showed a resilient trait, subtle changes were detected in microbial community composition and function, and this may be related to the increase in yield observed.

Gluconacetobacter diazotrophicus Changes The Molecular Mechanisms of Root Development in Oryza sativa L. Growing Under Water Stress.

BACKGROUND: Inoculation with Gluconacetobacter diazotrophicus has shown to influence root development in red rice plants, and more recently, the induced systemic tolerance (IST) response to drought was also demonstrated. The goal of this study was to evaluate the inoculation effect of G. diazotrophicus strain Pal5 on the amelioration of drought stress and root development in red rice (Oryza sativa L.). METHODS: The experimental treatments consist of red rice plants inoculated with and without strain Pal5 in presence and absence of water restriction. Physiological, biochemical, and molecular analyses of plant roots were carried out, along with measurements of growth and biochemical components. RESULTS: The plants showed a positive response to the bacterial inoculation, with root growth promotion and induction of tolerance to drought. An increase in the root area and higher levels of osmoprotectant solutes were observed in roots. Bacterial inoculation increased the drought tolerance and positively regulated certain root development genes against the water deficit in plants. CONCLUSION: G. diazotrophicus Pal5 strain inoculation favored red rice plants by promoting various root growth and developmental mechanisms against drought stress, enabling root development and improving biochemical composition.

Phosphate-Solubilizing Bacteria with Low-Solubility Fertilizer Improve Soil P Availability and Yield of Kikuyu Grass.

Inoculation with phosphate-solubilizing bacteria (PSB) and the application of phosphorus (P) sources can improve soil P availability, enhancing the sustainability and efficiency of agricultural systems. The implementation of this technology in perennial grasses, such as Kikuyu grass, for cattle feed in soils with high P retention, such as Andisols, has been little explored. The objective of this study was to evaluate the productive response of Kikuyu grass and soil P dynamics to BSF inoculation with different P sources. The experiment was conducted on a Kikuyu pasture, which was evaluated for 18 months (September 2020 to March 2022). Three P fertilizers with different solubility levels were applied: diammonium phosphate (DAP) (high-solubility), rock phosphate (RP), and compost (OM) (low-solubility). Moreover, the inoculation of a PSB consortium (Azospirillum brasilense D7, Rhizobium leguminosarum T88 and Herbaspirillum sp. AP21) was tested. Inoculation with PSB and fertilization with rock phosphate (RP) increased soil labile P and acid phosphomonoesterase activity. Increased grass yield and quality were related with higher soil inorganic P (Pi) availability. This study validated, under field conditions, the benefits of PSB inoculation for soil P availability and Kikuyu grass productivity.

Co-Inoculation of Plant-Growth-Promoting Bacteria Modulates Physiological and Biochemical Responses of Perennial Ryegrass to Water Deficit.

Perennial ryegrass is a forage commonly used in temperate regions for livestock feeding; however, its yield is affected by reduced biomass production under water deficit. In a previous study, three co-inoculations of beneficial bacteria were selected based on their ability to promote plant growth under reduced water availability. The aim of this work was to elucidate some mechanisms by which the selected bacteria can help improve the response of perennial ryegrass to water deficit. Ryegrass plants were inoculated with each of the co-inoculations (Herbaspirillum sp. AP02−Herbaspirillum sp. AP21; Herbaspirillum sp. AP02−Pseudomonas sp. N7; Herbaspirillum sp. AP21−Azospirillum brasilense D7) and subjected to water deficit for 10 days. Physiological and biochemical measurements were taken 10 days after stress and shortly after rehydration. The results showed that bacteria had a positive effect on shoot biomass production, dissipation of excess energy, and proline and chlorophyll pigments during the days of water deficit (p < 0.05). The leaf water status of the inoculated plants was 12% higher than that of the uninoculated control after rehydration. Two Herbaspirillum strains showed greater potential for use as biofertilizers that help ameliorate the effects of water deficit.

The genome of Bacillus coahuilensis reveals adaptations essential for survival in the relic of an ancient marine environment.

The Cuatro Ciénegas Basin (CCB) in the central part of the Chihuahan desert (Coahuila, Mexico) hosts a wide diversity of microorganisms contained within springs thought to be geomorphological relics of an ancient sea. A major question remaining to be answered is whether bacteria from CCB are ancient marine bacteria that adapted to an oligotrophic system poor in NaCl, rich in sulfates, and with extremely low phosphorus levels (<0.3 microM). Here, we report the complete genome sequence of Bacillus coahuilensis, a sporulating bacterium isolated from the water column of a desiccation lagoon in CCB. At 3.35 Megabases this is the smallest genome sequenced to date of a Bacillus species and provides insights into the origin, evolution, and adaptation of B. coahuilensis to the CCB environment. We propose that the size and complexity of the B. coahuilensis genome reflects the adaptation of an ancient marine bacterium to a novel environment, providing support to a "marine isolation origin hypothesis" that is consistent with the geology of CCB. This genomic adaptation includes the acquisition through horizontal gene transfer of genes involved in phosphorous utilization efficiency and adaptation to high-light environments. The B. coahuilensis genome sequence also revealed important ecological features of the bacterial community in CCB and offers opportunities for a unique glimpse of a microbe-dominated world last seen in the Precambrian.

Potential of Herbaspirillum and Azospirillum Consortium to Promote Growth of Perennial Ryegrass under Water Deficit.

Plant growth-promoting bacteria (PGPB) can mitigate the effect of abiotic stresses on plant growth and development; however, the degree of plant response is host-specific. The present study aimed to assess the growth-promoting effect of Herbaspirillum (AP21, AP02), Azospirillum (D7), and Pseudomonas (N7) strains (single and co-inoculated) in perennial ryegrass plants subjected to drought. The plants were grown under controlled conditions and subjected to water deficit for 10 days. A significant increase of approximately 30% in dry biomass production was observed using three co-inoculation combinations (p < 0.01). Genomic analysis enabled the detection of representative genes associated with plant colonization and growth promotion. In vitro tests revealed that all the strains could produce indolic compounds and exopolysaccharides and suggested that they could promote plant growth via volatile organic compounds. Co-inoculations mostly decreased the in vitro-tested growth-promoting traits; however, the co-inoculation of Herbaspirillum sp. AP21 and Azospirillum brasilense D7 resulted in the highest indolic compound production (p < 0.05). Although the Azospirillum strain showed the highest potential in the in vitro and in silico tests, the plants responded better when PGPB were co-inoculated, demonstrating the importance of integrating in silico, in vitro, and in vivo assessment results when selecting PGPB to mitigate drought stress.

First record of the interaction between the arthropod-pathogenic fungus Gibellula and a new species of harvestman Auranus (Stygnidae) narrowly endemic to the Brazilian rain forest.

Harvestmen are one of the largest groups of arachnids with more than 6,500 species distributed in 1,500 genera and 50 families. However, the interactions between harvestmen and arthropod-pathogenic fungi have rarely been studied. Certain previous studies report that fungal attack represents one of the most important factors for the mortality of harvestmen, but the fungus has rarely been identified, and most of the important information about the fungus-host interactions remains unrecorded. In the present study, we have described the new species Auranus quilombola sp. nov. and reported its interactions with the arthropod-pathogenic fungus Gibellula sp. Auranus quilombola sp. nov. belongs to the family Stygnidae, and it is endemic to the humid mountain forests of Cear state, Brazil in an area of endemism known as Brejos Cearenses. The species is related to five other species of Auranus, all of which have been recorded from the Amazon rainforest. A taxonomic description of this new species and its biogeographic implications have also been discussed in this paper.

Notes on the "Pinocchio-cobweb-spider" Craspedisia cornuta (Keyserling, 1891) from southeastern of Brazil (Theridiidae, Pholcommatinae).

Craspedisia cornuta (Keyserling, 1891), is redescribed on the basis of SEM data after more than fifty years after its last records. We also provide information on its natural history. SEM images for the proboscis, ventral plates of abdomen and male palp and epigynal plate are provided. Data on natural history using specimens collected in the Serra do Japi, from the state of São Paulo were analyzed and presented for the first time for this little-known species of Pholcommatinae theridiid spider.

Dry-Caribbean Bacillus spp. Strains Ameliorate Drought Stress in Maize by a Strain-Specific Antioxidant Response Modulation.

Drought is a global problem for crop productivity. Therefore, the objective of this research was to evaluate five dry-Caribbean Bacillus spp. strains in drought stress amelioration in maize plants. Maize seeds were single-strain inoculated and sown in pots under greenhouse conditions. After 12 days, plants were subjected to 33 days of drought conditions, i.e., 30% of soil field capacity, and then collected to measure leaf and root dry biomass, plant height, antioxidant enzymes, proline accumulation, and P+, Ca2+, and K+ uptake. Results correlated drought stress amelioration with the inoculation of Bacillus spp. strains XT13, XT38 and XT110. Inoculated plants showed increases in dry biomass, plant height, and K+ and P+ uptake. The overall maize antioxidant response to bacterial inoculation under drought stress showed dependence on proline accumulation and decreases in ascorbate peroxidase and glutathione reductase activities. Moreover, results suggest that this stress amelioration is driven by a specific plant-strain correlation observed in antioxidant response changes in inoculated plants under stress. Also, there is a complex integration of several mechanisms, including plant growth-promotion traits and nutrient uptake. Hence, the use of dry-Caribbean plant growth-promoting Bacillus strains represents an important biotechnological approach to enhance crop productivity in arid and semi-arid environments.

Conura baturitei sp. nov. (Hymenoptera: Chalcididae): a hyperparasitoid of spiders through Zatypota riverai (Hymenoptera: Ichneumonidae).

Conura, the largest genus of Chalcididae (Hymenoptera: Chalcidoidea), is mostly distributed in the New World where 295 of the 301 described species occur. Chalcididae are in some cases hyperparasitoids of insects. In this study, we report the unusual association of the hyperparasitoid Conura baturitei sp. nov. with spider species of the genus Theridion Walckenaer (Theridiidae) through Zatypota riverai Gauld (Ichneumonidae, Pimplinae, Polysphincta genus-group), a primary ectoparasitoid of spiders. The new species is described and illustrated, and the host-parasitoid-hyperparasitoid interaction is discussed.

Niche partitioning and coexistence of two spiders of the genus Peucetia (Araneae, Oxyopidae) inhabiting Trichogoniopsis adenantha plants (Asterales, Asteraceae).

Niche theory suggests that the coexistence of ecologically similar species in the same site requires some form of resource partitioning that reduces or avoids interspecific competition. Here, from July 2013 to December 2015, we investigated spatial niche differentiation at three different scales of two sympatric congeneric spiders, Peucetia rubrolineata and P. flava, along an altitudinal gradient in shaded and open areas in an Atlantic forest in Serra do Japi, SP, Brazil. These spiders are peculiar in that they present an exclusive association with the plant Trichogoniopsis adenantha (Asteraceae). In theory, the coexistence of two Peucetia species could be explained by: (1) microhabitat segregation with individuals from different species occupying different parts of the same plants; (2) mesohabitat segregation with different species using plant in different environments; (3) macrohabitat segregation, where different species would not co-occur along the altitudinal gradient. With respect to micro-habitat use, in both species, different instars used different plant parts, while the same instars of both species used the same type of substrate. However, the two Peucetia species segregated by meso-habitat type, with P. rubrolineata preferring T. adenantha plants in shaded areas and P. flava preferring those in open areas. Our results support the hypothesis of niche partitioning begetting diversity, and highlight the importance of analyzing habitat use at multiple scales to understand mechanisms related to coexistence.

Two new species of Zatypota (Hymenoptera: Ichneumonidae, Pimplinae) sharing the same host spider in Northeast Brazil.

 Some polysphinctine wasps of the genus Zatypota complete their life cycles upon theridiid host spiders. The host range of these wasps is usually species-specific, although in some less common associations more than one wasp species interacts with the same host spider. Here we describe and illustrate the polysphinctine wasps Zatypota baezae sp. n. and Zatypota mulunguensis sp. n. (Hymenoptera: Ichneumonidae), both koinobiont ectoparasitoids of the spider Anelosimus baeza (Theridiidae). The two parasitoid wasps show the same development time (12 days) which was longer when compared with other parasitoid wasps Z. anomala Holmgren and Z. riverai Gauld (nine days). As described for other species of Zatypota and Hymenoepimecis, the second larval instar remains attached to the spider by the remains of the chorion and also by a rigid brownish-semitransparent membrane called a saddle.

Macrophyes pacoti n. sp. (Araneae: Anyphaenidae) from Brazilian Atlantic Forest, with notes on an araneopathogenic fungus.

The spider genus Macrophyes O. Pickard-Cambridge, 1893 includes five species from the Neotropical region (World Spider Catalog 2019). Two species were described from Central America, M. attenuata, the type species, by Pickard-Cambridge (1893), known until now only by the male, and M. elongata by Chickering (1937) know by both sexes. Three other species were described from South America, M. silvae Brescovit, 1992 and M. manati Brescovit, 1993 from Peru, and M. jundiai Brescovit, 1993 from Brazil (Brescovit 1992, 1993). Brescovit (1997) diagnosed this genus from other Anyphaeninae by the cylindrical abdomen, retrolateral margin of the chelicera with prominent distal tooth, close to the claw and by the tibia of the male palp almost twice longer than the cymbium. The females could be confused with Mesilla Simon by the long and cylindrical abdomen, but are distinguished by the epigynum with narrow, sinuous lateral borders and, internally, by the long copulatory ducts (see Brescovit, 1997: figs 146, 150-151).

The wasp Flacopimpla varelae Gauld (Ichneumonidae: Pimplinae), parasitoid of the spider Achaearanea tingo Levi (Theridiidae: Theridiinae), with description of the male wasp.

Parasitoid organisms can manipulate the morphology, physiology and/or behavior of their hosts to increase their own survival (Moore 2002; Korenko et al. 2015a). Wasps of the Polysphincta genus-group sensu Gauld Dubois, 2006 (hereafter polysphinctine wasps) are well known to act exclusively as koinobiont ectoparasitoids of spiders (Gauld Dubois 2006). The host range of these wasps is remarkably narrow and often species-specific; individuals of some polysphinctine genera (e.g. Hymenoepimecis, Acrotaphus) usually attack orb-weaver spiders (Pádua et al. 2016), whereas other are specialized on spiders that construct three-dimensional webs. Fritzén (2014), for example, discussed that Oxyrrhexis Föerster, 1869, Zatypota Föerster, 1869 and Flacopimpla Gauld, 1991 are specialized on theridiid hosts, the last two mainly or exclusively on spiders of the subfamily Theridiinae.

Effect of phosphate-solubilizing bacteria on phosphorus dynamics and the bacterial community during composting of sugarcane industry waste.

Sugarcane processing generates a large quantity of residues, such as filter cake and ashes, which are sometimes composted prior to their amendment in soil. However, important issues still have to be addressed on this subject, such as the description of bacterial succession that occurs throughout the composting process and the possibilities of using phosphate-solubilizing bacteria (PSB) during the process to improve phosphorus (P) availability in the compost end product. Consequently, this study evaluated the bacterial diversity and P dynamics during the composting process when inoculated with Pseudomonas aeruginosa PSBR12 and Bacillus sp. BACBR01. To characterize the bacterial community structure during composting, and to compare PSB-inoculated compost with non-inoculated compost, partial sequencing of the bacterial 16S rRNA gene and sequential P fractionation were used. The data indicated that members of the order Lactobacillales prevailed in the early stages of composting for up to 30 days, mostly due to initial changes in pH and the C/N ratio. This dominant bacterial group was then slowly replaced by Bacillales during a composting process of up to 60 days. In addition, inoculation of PSB reduced the levels of Ca-bound P by 21% and increased the labile organic P fraction. In PSB-inoculated compost, Ca-P compound solubilization occurred concomitantly with an increase of the genus Bacillus. The bacterial succession and the final community is described in compost from sugarcane residues and the possible use of these inoculants to improve P availability in the final compost is validated.

Characterization of diazotrophic phosphate solubilizing bacteria as growth promoters of maize plants / Caracterización de bacterias diazotróficas solublizadoras de fosfato como promotoras de crecimiento en plantas de maíz

Phosphorus is limiting for growth of maize plants, and because of that use of fertilizers like rock phosphate has been proposed. However, direct use of rock phosphate is not recommended because of its low availability, so it is necessary to improve it. In this study, a group of diazotrophic bacteria were evaluated as phosphate-solubilizing bacteria, for their production of indolic compounds and for their effects on growth of maize plants. Strains of the genera Azosporillum, Azotobacter, Rhizobium and Klebsiella, were quantitatively evaluated for solubilization of Ca3(PO4)2 and Rock Phosphate as a single source of phosphorous in SRS culture media. Additionally, the phosphatase enzyme activity was quantified at pH 5.0, 7.0 and 8.0 using p-nitrophenyl phosphate, and production of indolic compounds was determined by colorimetric quantification. The effect of inoculation of bacteria on maize was determined in a completely randomized greenhouse experiment where root and shoot dry weights and phosphorus content were assessed. Results showed that strain C50 produced 107.2 mg.L-1 of available-P after 12 days of fermentation, and AC10 strain had the highest phosphatase activity at pH 8 with 12.7 mg of p-nitrophenol mL.h-1. All strains synthetized indolic compounds, and strain AV5 strain produced the most at 63.03 µg.mL-1. These diazotrophic bacteria increased plant biomass up to 39 % and accumulation of phosphorus by 10%. Hence, use of diazotrophic phosphate-solubilizing bacteria may represent an alternative technology for fertilization systems in maize plants.

El fósforo es limitante para el crecimiento de plantas de maíz y debido a eso se ha propuesto el uso de fertilizantes como la roca fosfórica. Sin embargo, el uso directo de roca fosfórica no es recomendado por su baja solubilidad, por lo que es necesario mejorarlo. En este estudio, un grupo de bacterias diazotróficas fueron evaluadas como bacterias solubilizadoras de fosfato, productoras de compuestos indólicos y sus efectos sobre el crecimiento de plantas de maíz. Cepas de los géneros Azospirillum, Azotobacter, Rhizobium y Klebsiella fueron evaluadas cuantitativamente en la solubilización de Ca3(PO4)2 y roca fosfórica como única fuente de fósforo en medio de cultivo SRS. Adicionalmente, la actividad de la enzima fosfatasa fue cuantificada a pH 5.0, 7.0 y 8.0 usando p-nitrofenil fosfato y, la producción de compuestos indólicos fue determinada por cuantificación colorimétrica. El efecto de la inoculación de las bacterias sobre plantas de maíz fue determinado en un experimento en invernadero con un diseño completamente al azar donde los pesos secos de raíz y hojas y el contenido de fósforo fueron evaluados. Los resultados mostraron que la cepa C50 produjo 107.2 mg.L-1 de fósforo disponible después de 12 días de fermentación y que la cepa AC10 tuvo la más alta actividad fosfatasa a pH 8 con 12.7 mg de p-nitrofenol mL.h-1. Todas las cepas sintetizaron compuestos indólicos y la cepa AV5 produjo la más alta cantidad con 63.03 µg.mL-1. Estas bacterias diazotróficas incrementaron la biomasa de las plantas por encima del 39 % y de la acumulación de fósforo por el 10 %. Aquí, el uso de bacterias diazotróficas solubilizadoras de fosfato puede representar una alternativa tecnológica para los sistemas de fertilización en plantas de maíz.