Chitinolytic Bacteria Research Articles

Composting of Cow-Dung-Amended Soil by the Dung Beetle Catharsius molossus L. Improves Bacterial Ecological Functions Related to Nitrogen Mineralization and Human and Plant Pathogenesis

The Asian dung beetle (Catharsius molossus L.; Coleoptera: Scarabeidae) has been shown to positively affect soil bacterial diversity and the agronomic features of crop plants. In this study, we used bioinformatic tools to investigate the differences in bacterial functional phenotypes and ecological functions between control soil, cow dung-amended soil (CD), and cow dung-amended soil composted by dung beetles (DB). The soil bacterial metagenomes were sequenced and analyzed with the bioinformatic packages BugBase, PICRUSt2, Tax4Fun, and FAPROTAX to evaluate the effects of dung beetle-mediated composting on bacterial functions such as human and plant pathogenicity, trophic strategies, and soil nutrient transformation. BugBase proved useful for the determination of differences in major functional phenotypes, whereas FAPROTAX was effective at identifying differences in bacterial ecological functions between the treatments. Both tools suggested a relative decrease in human pathogens in the DB soil. This was corroborated by the pairwise comparison of abundances in bacterial species, which showed a significant reduction in the abundance of the broad-host-range pathogen Pseudomonas aeruginosa in the DB soil. In addition, FAPROTAX suggested a decrease in plant pathogens and an increase in chitinolytic bacteria, meaning that the DB treatment might be beneficial to the plant-growth-promoting bacteria involved in biological control. Finally, FAPROTAX revealed an array of ecological functions related to trophic strategies and macro- and micronutrient metabolism. According to these results, the activity of C. molossus beetles enhanced methanotrophy, ammonification, nitrification, sulfate reduction, and manganese oxidation, whereas iron respiration was decreased in the DB-treated soil. Our results represent a collection of general insights into the effects of C. molossus beetles on soil bacterial functions, which also reflect on the nutrient composition of dung beetle-composted soil.

Eksplorasi Mikroflora Alami Cairan Nepenthes mirabilis (Lour) Druce di Kawasan Hutan Penelitian dan Pendidikan Biologi Universitas Andalas

Indonesia is a country that is rich in flora and fauna diversity, one of the unique flora in Indonesia is Nepenthes. This bag serves to trap insects or other small animals, the Biology Education and Research Forest (HPPB) is located in the Andalas Limau Manis University campus area which is classified as lowland tropical rain forest which is the habitat of Nepenthes, in the Biology Education and Research Forest (HPPB) this type of pitcher plant, namely Nepenthes mirabilis. Nepenthes mirabilis is a plant that is able to digest insects trapped in pockets at the ends of its leaf tendrils, so it is classified as a carnivorous plant. Microorganisms play an important role in breaking down organic materials into inorganic ones available to plants. Types of bacteria and bacterial populations greatly determine the decomposition process of animals that have been trapped in the bag as a source of nutrients for Nepenthes plants. This study aims to explore the natural microflora of Nepenthes mirabilis fluids, determine the proportional presence of potential bacteria, and determine the in vitro potential of chitinolytic bacteria from Nepenthes mirabilis fluids. This study used a survey method which was analyzed descriptively. The results showed that Nepenthes mirabilis fluid contained the presence of Fermentative, Amylolytic, Proteolytic, Chitinolytic and Lipolitical bacteria. Nepenthes mirabilis liquid in open bags contained chitinolytic bacteria, the highest presence of chitinolytic bacteria was found in MBB samples (20,104 cfu/ml) and MBA samples (18,104 cfu/ml). .28), fermentative (2.33 and 2.00), amylolytic (1.42 and 1.28), proteolytic (2.00 and 2.00), lipolytic (1.75 and 1.28).

Chitin Degradation by Microbial Communities of the Kandalaksha Gulf, White Sea

Chitin is among the most widespread biopolymers on Earth and occurs in high quantities in the exoskeletons of marine invertebrates. Chitinolytic bacteria are therefore typical components of marine ecosystems and play an important part in chitin biodegradation. The Kandalaksha Gulf area near the White Sea Biological Station, Moscow State University, which is inhabited by numerous invertebrates, is a promising site for the isolation of such bacteria. The composition of environmental prokaryotic communities and of enrichment cultures grown on chitin was determined, and pure cultures of active chitinolytics were isolated and identified as Pseudoalteromonas undina and Vibrio alginolyticus. The chitinolytic potential of the genera predominant in enrichment cultures was assessed; these may include previously unknown chitinolytic microorganisms.

Isolation, Plant Growth-Promoting Properties, and Whole-Genome Sequence of a Novel Paenibacillus Species.

This work aimed to isolate and characterize a novel chitin-degrading bacterium from Yok Don National Park, Vietnam, for crop production studies. Among the chitinolytic isolates, strain YSY-4.3 was selected, which grew rapidly and produced a large halo around the colony. 16S rDNA analysis indicated that the strain is a novel species in the genus Paenibacillus, and an in vitro evaluation showed that the strain produced phytohormones (IAA, GA3, and zeatin), biofilms, and siderophores; possessed cellulase; and exerted antifungal activity. The whole genome of the strain was 5,628,400 bp with 49.3% GC content, 5056 coding sequences, 48 tRNA, and 1 rRNA. It shared the highest values of digital DNA-DNA hybridization (67.4%) and average nucleotide identity (89.54%) with those of Paenibacillus woosongensis B2_4 (CP126084.1), suggesting a novel species. Of the coding sequences, 4287 proteins were identified by COG, and 2561 were assigned by KEGG. The genome contained at least 51 genes involved in plant growth and resistance to heavy-metal toxicity and 359 carbohydrate-active enzymes. The chitinolytic system of the strain was composed of 15 enzymes, among them, PsChiC, which contained a GH18 catalytic domain and a GH5 catalytic domain, had not been previously reported. In addition, the genome possessed 15 gene clusters encoding antimicrobial metabolites, 10 of which are possible novel clusters. This study expands knowledge regarding novel chitinolytic bacteria from Yok Don National Park and provides a valuable gene resource for future studies.

Biocontrol potential of cell-free supernatant of Paenibacillus chitinolyticus against Plasmodiophora brassicae in two important Brassica species

Plasmodiophora brassicae is a serious threat to Brassica crops worldwide, resulting in substantial economic losses for growers. Biocontrol with chitinolytic bacteria producing chitinase is gaining attention as a natural alternative to chemicals. This approach is favored due to the essential role chitinases play in protecting against chitin-containing pathogens. Given that chitin is a major component in the resting spores of P. brassicae and plays a crucial role during pathogenesis, it is probable that Paenibacillus chitinolyticus, producing a high level of chitinase, could suppress P. brassicae by targeting chitin in a critical stage of this pathogen’s life cycle. Our research aimed to evaluate the effect of various applications of P. chitinolyticus on clubroot suppression in two economically important Brassica species: Chinese cabbage and rapeseed. The effectiveness of the cell-free supernatant (CFS) of an endemic strain of P. chitinolyticus from the Czech Republic at five different time points was studied in the greenhouse by measuring the disease severity index. Early application of P. chitinolyticus decreased the disease index significantly within both plant species resulting in increased shoot dry weight. In conclusion, the CFS of P.chitinolyticus has significant antagonistic activity against clubroot in Chinese cabbage and rapeseed in the early developmental stages of clubroot occurrence and holds the potential as a biofertilizer as well as bioprotectant agent in clubroot management of P. brassicae.

A novel N-acetylglucosamine-6-phosphate deacetylase that is essential for chitin utilization in the chitinolytic bacterium, Chitiniphilus shinanonensis.

We aimed to investigate the function of an unidentified gene annotated as a PIG-L domain deacetylase (cspld) in Chitiniphilus shinanonensis SAY3. cspld was identified using transposon mutagenesis, followed by negatively selecting a mutant incapable of growing on chitin, a polysaccharide consisting of N-acetyl-d-glucosamine (GlcNAc). We focused on the physiological role of CsPLD protein in chitin utilization. Recombinant CsPLD expressed in Escherichia coli exhibited GlcNAc-6-phosphate deacetylase (GPD) activity, which is involved in the metabolism of amino sugars. However, SAY3 possesses two genes (csnagA1 and csnagA2) in its genome that code for proteins whose primary sequences are homologous to those of typical GPDs. Recombinant CsNagA1 and CsNagA2 also exhibited GPD activity with 23 and 1.6% of catalytic efficiency (kcat/Km), respectively, compared to CsPLD. The gene-disrupted mutant, Δcspld was unable to grow on chitin or GlcNAc, whereas the three mutants, ΔcsnagA1, ΔcsnagA2, and ΔcsnagA1ΔcsnagA2 grew similarly to SAY3. The determination of GPD activity in the crude extracts of each mutant revealed that CsPLD is a major enzyme that accounts for almost all cellular activities. Deacetylation of GlcNAc-6P catalyzed by CsPLD (but not by typical GPDs) is essential for the assimilation of chitin and its constituent monosaccharide, GlcNAc, as a carbon and energy source in C. shinanonensis.

Characterization of Chitinolitic Bacteria from Hermatia illucent Larvae Waste: Antifungal Activity, Hydrolytic Enzyme, and Phosphate-Potassium Solubilization

Hermetia illucens larvae, also known as the black soldier fly larvae, are best known as the decomposers of organic matter. There are many potential microbes found in the feces of BSF larvae. This research aimed to isolate the chitinolytic bacteria from chicken manure maggot waste, identify the antifugal activity, hydrolytic enzyme activity, phosphate and potassium solubilization, and bacterial species through 16S rRNA gene analysis. The initial screening focused on bacteria with chitinolytic ability. Antifungal activity tests were performed against phytopathogenic fungi, Colletotrichum sp. Isolate MKP02 showed the highest activity in inhibiting the growth of Colletotrichum sp. up to 100% and produced protease and cellulase enzymes, along with the ability to solubilize potassium. Furthermore, the potential isolate MKP04, the isolate shows the highest cellulolytic activity with a percentage of 300%. It can inhibit Colletotrichum sp. fungi, as well as having lipase enzyme content, and being able to dissolve potassium. The results of 16S rRNA gene amplification on the two isolates showed that both isolates were close to bacteria of the genus Lysinibacillus and Brevibacterium. This research is expected to provide valuable information about the bacterial content, levels of hydrolytic enzymes, and the ability to solubilize phosphate and potassium in BSF.

Farmed Insect Frass as a Future Organic Fertilizer

The aim of this incubation experiment was to evaluate the effect of Tenebrio molitor L. frass on selected chemical and microbiological properties of acid peat. The optimal rate of mealworm frass in the substrate for growing ornamental trees and shrubs was determined. Acid peat was fertilized with frass or urea at five nitrogen (N) rates: 0, 50, 100, 200, and 400 mg dm−3. Mineral N content and electrical conductivity increased, and calcium content decreased in peat with increasing N rates. Similarly to urea, frass increased the ammonification rate at the beginning of incubation and the nitrification rate from the second week of incubation. Higher frass rates increased the abundance of plant-available nutrients (N, P, Mg, K, and Na) in acid peat. Frass undesirably decreased the counts of bacteria with antagonistic activity against soil-borne plant pathogens. Regarding the abundance of functional genes, the optimal N rate was 100 mg dm−3, which promoted the growth of N-fixing and chitinolytic bacteria. Higher N rates promoted the development of aerobic spore-forming bacteria, which produce antibiotics that can be used as biocontrol agents. Moderate fertilizer rates contributed to N accumulation in bacterial biomass. These preliminary findings, which indicate that insect frass can partially replace mineral fertilizers, are promising and can be used in pot and field experiments testing various plant species.

Antibiotic resistance and molecular identification of dominant bacteria associated with loose shell syndrome in mangrove crabs (Scylla spp.)

The emergence of loose shell syndrome (LSS) in Philippine mangrove crabs poses a serious threat to both the aquaculture industry and the delicate ecosystems it relies on. This study aimed to identify dominant bacteria associated with LSS and assess their antibiotic resistance to guide treatment and prevention strategies while safeguarding public health. Mangrove crab samples with loose carapace were collected from the province of Capiz, Philippines. Dominant bacteria that grew on Thiosulfate– Citrate–Bile Salts–Sucrose (TCBS) and modified chitin agar were isolated and identified by sequencing of the16S rRNA. Antibiotic susceptibility of the dominant bacterial isolates was performed using the agar disk diffusion method. Dominant bacteria that grew on TCBS agar included putative Vibrio, Proteus, Shewanella, and Stutzerimonas. The isolates had antibiotic resistance indices (ARI) ranging 0.8 to 1.2. Chitinolytic bacteria were dominated by Vibrio, Shewanella, and Brevundimonas. Both Vibrio and Brevundimonas exhibited resistance to gentamicin, ciprofloxacin, and norfloxacin, while Shewanella showed resistance to ciprofloxacin. The presence of multi-drug resistant bacteria in LSS-affected crabs highlights the urgent need for effective health management strategies in the industry while mitigating the risks associated with antibiotic resistance to protect both the sustainability of mangrove crab aquaculture and the health of consumers.

ISOLASI DAN PEMANFAATAN BAKTERI KITINOLITIK DARI CANGKANG UDANG PUTIH (PENAEUS MERGUENSIS) DALAM MENGHASILKAN ENZIM KITINASE

Indonesia is listed as the third largest shrimp producing country in the world. Shrimp is one of the leading export commodities. Shrimp is one of the main commodities in the fishing industry. Thus encouraging Indonesia to become one of the shrimp producing countries. In the shrimp processing process, usually the heads and shells of the shrimp are thrown away or used as animal feed. Traditionally, shrimp shell waste is generally used as a mixture for making crackers, paste, shrimp paste and as additional animal feed and returned to the shrimp cultivation itself. One use of shrimp shell waste that has prospects for development and has quite high economic value is processing it into chitin, chitosan and glucosamine. The aim of this research is to obtain isolates of chitinolytic bacteria from isolation and to utilize chitinolytic bacteria from white shrimp (Penaeus merguensis) shells to produce chitinase enzymes. Chitinolytic bacteria are bacteria that produce chitinase enzymes which play a role in degrading chitin into oligomers and chitin derivative compounds. Chitinolytic bacteria can be obtained from various sources such as the rhizosphere, phyllosphere, soil or from water environments such as seas, lakes, ponds or shrimp ponds and so on. Chitin that exists in nature is easily degraded by microorganisms. There are two pathways in the chitin degradation process. First, degradation by chitinolytic which hydrolyzes the ?-1,4-glycoside bond. Second, the polymer undergoes first deacetylation and then hydrolysis by chitosanase. Chitinase has many benefits, including as a bioinsecticide and biofunctional agent in controlling plant pests and is used to process chitin waste in the shrimp and crab freezing industry. It can also be used in the medical and food fields. From the test results, three types of bacteria were obtained, namely Vibrio sp, Bacillus sp, and Pseudomonas sp.

Sustainable valorizing high-protein feather waste utilization through solid-state fermentation by keratinase-enhanced Streptomyces sp. SCUT-3 using a novel promoter

Feather waste, a rich source of proteins, has traditionally been processed through high-temperature puffing and acid-base hydrolysis, contributing to generation of greenhouse gases and H2S. To address this issue, we employed circular economy techniques to recover the nutritional value of feather waste. Streptomyces sp. SCUT-3, an efficient proteolytic and chitinolytic bacterium, was isolated for feather degradation previously. This study aimed to valorize feather waste for feed purposes by enhancing its feather transformation ability through promoter optimization. Seven promoters were identified through omics analysis and compared to a common Streptomyces promoter ermE*p. The strongest promoter, p24880, effectively enhanced the expression of three candidate keratinases (Sep39, Sep40, and Sep53). The expression efficiency of double-, triple-p24880 and sandwich p24880-sep39-p24880 promoters were further verified. The co-overexpression strain SCUT-3-p24880-sep39-p24880-sep40 exhibited a 16.21-fold increase in keratinase activity compared to the wild-type. Using this strain, a solid-state fermentation process was established that increased the feather/water ratio (w/w) to 1:1.5, shortened the fermentation time to 2.5 days, and increased soluble peptide and free amino acid yields to 0.41 g/g and 0.14 g/g, respectively. The resulting has high protein content (90.49 %), with high in vitro digestibility (94.20 %). This method has the potential to revolutionize the feather waste processing industry.

Isolation and characterization of bacteria from the gut of a mesopelagic copepod Cephalophanes reflugens (Copepoda: Calanoida)

Abstract The mesopelagic calanoid copepod Cephalophanes reflugens is characterized by its large eyes with semi-parabolic reflectors. It is hypothesized that the eyes aid in finding crustacean carcasses as food in poor deep-sea light and oligotrophic conditions. Here, the crustacean carcasses-associated luminous, chitin-degrading bacteria may play a vital role in detecting and digesting foods by the copepod. In this study, we collected adult female C. reflugens (n = 9) from the mesopelagic layers off southwestern Japan in the Pacific Ocean and obtained a total of 47 bacterial isolates from the gut contents. None of the isolates were luminescent, but almost half of the isolates were chitinolytic. Based on the 16S rRNA gene sequences, these chitinolytic bacteria were identified as members of the genus Vibrio, Photobacterium and Pseudoalteromonas. In culture experiments at 15°C, most of the chitinolytic isolates efficiently utilized colloidal chitin as the sole carbon source and degraded the carapace strip of shrimp (Litopenaeus vannamei). Some isolates showed these chitinoclastic activities even at low temperatures (<5°C), equivalent to that of the deep-sea waters. The present results imply that chitin-degrading bacteria significantly contribute to chitin digestion in the gut of C. reflugens, whereas the involvement of luminous bacteria in the feeding mechanism remains unidentified.

Isolation, screening, and identification of chitinase-producing bacterial strains from riverbank soils at Ambo, Western Ethiopia

Chitinases are hydrolytic enzymes that dissolve the glycosidic linkages in chitin. Chitin is a cell wall component of fungi and fund in exoskeleten of worms and arthropods. Chitinase has been applied in agriculture, as a biopesticide for the control of plant fungal infections, in medicine, and in waste management. This research aimed to isolate, screen, and identification of chitinase-producing bacteria from riverbank soils. Twenty nine chitinolytic bacteria were isolated from the river bank soil samples, from which 9 of them had strong chitinolytic properties. Chitinase production was determined by zones of hydrolysis produced after 96 h of incubation at 37 °C. The different bacterial isolates were characterized morphologically, microscopically, and biochemically and finally eight strain were identified at species level by Matrix Assisted Laser Desorption Ionization - Time of Flight Mass Spectrometry (MALDI–TOF MS). From the eight, bacterial isolates investigated in this study Stenotrophomonas maltophilia showed the highest chitinase enzyme activity (625 μg/mL) followed by Pseudomonas putida with the enzyme activity of (553 μg/mL) and the least enzyme activity was recorded for Lilliottia amnigena (80 μg/mL). An incubation temperature of 45 °C, neutral pH and an incubation period of 96 h are found to be the optimum condition for the chitinase enzyme production from Stenotrophomonas maltophilia. The results of this study indicated the possibility of the production of chitinase from the chitinolytic bacterial isolates, which was highly useful for a variety of applications, including biocontrol of harmful insects and pathogenic fungi as well as in the biochemical, pharmaceutical, and medical sectors.

Degradation of marine crustacean shell wastes through single-stage co-fermentation using proteolytic and chitinolytic bacteria.

Management of crustacean shell waste (SW) through an eco-friendly technique is an environmental obligation to control pollution. The present study showed a novel approach through the simultaneous application of proteolytic and chitinolytic bacteria to effectively degrade unprocessed crustacean SW. For this, the bacteria with concurrent chitinolytic and proteolytic activity (Bacillus subtilis, Priestia megaterium, or Bacillus amyloliquefaciens) were applied either alone or in combination with one proteolytic strain (Paenibacillus alvei) in the unprocessed lobster, crab, and shrimp SW. The method degraded the shells with high deproteinization (> 90%) and demineralization efficiency (> 90%). The degradation was confirmed through scanning electron microscopy. The highest weight loss achieved with shrimp, crab, and lobster shells was 93.67%, 82.60%, and 83.33%, respectively. B. amyloliquefaciens + P. alvei combination produced the highest weight loss in crab and lobster SW, whereas all combinations produced statistically similar weight loss in shrimp SW. There was a concurrent production of N-acetyl glucosamine (up to 532.89, 627.87, and 498.95 mg/g of shrimp, lobster, and crab shell, respectively, with P. megaterium + P. alvei and B. amyloliquefaciens + P. alvei in all SW) and amino acids (4553.8, 648.89, 957.27 μg/g of shrimp, lobster, and crab shells, respectively with B. subtilis + P. alvei in shrimp and B. amyloliquefaciens + P. alvei in crab and lobster). Therefore, it is concluded that, for the first time, efficient degradation of crustacean shell waste was observed using chitinolytic and proteolytic bacterial fermentation with the obtention of byproducts, providing a basis for further application in SW management.

Multi-enzyme Machinery for Chitin Degradation in the Chitinolytic Bacterium Chitiniphilus shinanonensis SAY3T.

The chitinolytic bacterium, Chitiniphilus shinanonensis SAY3T was examined to characterize its chitin-degrading enzymes in view of its potential to convert biomass chitin into useful saccharides. A survey of the whole-genome sequence revealed 49 putative genes encoding polypeptides that are thought to be related to chitin degradation. Based on an analysis of the relative quantity of each transcript and an assay for chitin-degrading activity of recombinant proteins, a chitin degradation system driven by 19 chitinolytic enzymes was proposed. These include sixteen endo-type chitinases, two N-acetylglucosaminidases, and one lipopolysaccharide monooxygenase that catalyzes the oxidative cleavage of glycosidic bonds. Among the 16 chitinases, ChiL was characterized by its remarkable transglycosylation activity. Of the two N-acetylglucosaminidases (ChiI and ChiT), ChiI was the major enzyme, corresponding to > 98% of the total cellular activity. Surprisingly, a chiI-disrupted mutant was still able to grow on medium with powdered chitin or GlcNAc dimer. However, its growth rate was slightly lower compared to that of the wild-type SAY3. This multi-enzyme machinery composed of various types of chitinolytic enzymes may support SAY3 to efficiently utilize native chitin as a carbon and energy source and may play a role in developing an enzymatic process to decompose and utilize abundant chitin at the industrial scale.

A novel endo-type chitinase possessing chitobiase activity derived from the chitinolytic bacterium, Chitiniphilus shinanonensis SAY3T.

One of the chitinases (ChiG) derived from the chitinolytic bacterium Chitiniphilus shinanonensis SAY3T exhibited chitobiase activity cleaving dimers of N-acetyl-D-glucosamine (GlcNAc) into monomers, which is not detected in typical endo-type chitinases. Analysis of the reaction products for GlcNAc hexamers revealed that all the five internal glycosidic bonds were cleaved at the initial stage. The overall reaction catalyzed by chitobiases toward GlcNAc dimers was similar to that catalyzed by N-acetyl-D-glucosaminidases (NAGs). SAY3 possesses two NAGs (ChiI and ChiT) that are thought to be important in chitin catabolism. Unexpectedly, a triple gene-disrupted mutant (ΔchiIΔchiTΔchiG) was still able to grow on synthetic medium containing GlcNAc dimers or powdered chitin, similar to the wild-type SAY3, although it exhibited only 3% of total cellular NAG activity compared to the wild-type. This indicates the presence of unidentified enzyme(s) capable of supporting normal bacterial growth on the chitin medium by NAG activity compensation.

Characterization of chitinolytic bacteria isolated from Ipomea pes caprae

Chitin has substantial benefits in several sectors including agriculture. In the plant protection field, chitin can promote the growth of certain bacteria which has possibly controlled the spread of fungal pathogens. Thus, chitinolytic bacteria producing chitinase enzymes can inhibit the growth of fungi. The purpose of this study was to examine the morphological and physiological characteristics of chitinolytic bacteria which collected from Ipomea pes caprae in Makassar and its ability to produce chitinolytic enzymes on medial culture. The method started to grow the isolates on the nutrient agar which were added to colloidal chitin. Furthermore, the bacteria were identified by its color, form, elevation and edge as well as tested its physiological characteristics with KOH 3% test and catalase test. In addition, bacterial chitinolytic index was carried out by using the disc diffusion method. The results showed that each isolate had yellowish white and grayish white colors; morphological characters: round and irregular colony shapes, colony edges smooth and choppy as well as umbonature and convex elevations. The physiological test results indicate that all isolates had a positive response in the catalase test, one of the isolates reacted positively to the gram test and the others reacted negatively to the test. Each isolate had chitinolytic activity with indices of 0.10, 0.09, 0.70, and 0.11.

Metagenomics uncovers dietary adaptations for chitin digestion in the gut microbiota of convergent myrmecophagous mammals.

In mammals, myrmecophagy (ant and termite consumption) represents a striking example of dietary convergence. This trait evolved independently at least five times in placentals with myrmecophagous species comprising aardvarks, anteaters, some armadillos, pangolins, and aardwolves. The gut microbiome plays an important role in dietary adaptation, and previous analyses of 16S rRNA metabarcoding data have revealed convergence in the composition of the gut microbiota among some myrmecophagous species. However, the functions performed by these gut bacterial symbionts and their potential role in the digestion of prey chitinous exoskeletons remain open questions. Using long- and short-read sequencing of fecal samples, we generated 29 gut metagenomes from nine myrmecophagous and closely related insectivorous species sampled in French Guiana, South Africa, and the United States. From these, we reconstructed 314 high-quality bacterial genome bins of which 132 carried chitinase genes, highlighting their potential role in insect prey digestion. These chitinolytic bacteria belonged mainly to the family Lachnospiraceae, and some were likely convergently recruited in the different myrmecophagous species as they were detected in several host orders (i.e., Enterococcus faecalis, Blautia sp.), suggesting that they could be directly involved in the adaptation to myrmecophagy. Others were found to be more host-specific, possibly reflecting phylogenetic constraints and environmental influences. Overall, our results highlight the potential role of the gut microbiome in chitin digestion in myrmecophagous mammals and provide the basis for future comparative studies performed at the mammalian scale to further unravel the mechanisms underlying the convergent adaptation to myrmecophagy. IMPORTANCE Myrmecophagous mammals are specialized in the consumption of ants and/or termites. They do not share a direct common ancestor and evolved convergently in five distinct placental orders raising questions about the underlying adaptive mechanisms involved and the relative contribution of natural selection and phylogenetic constraints. Understanding how these species digest their prey can help answer these questions. More specifically, the role of their gut microbial symbionts in the digestion of the insect chitinous exoskeleton has not been investigated in all myrmecophagous orders. We generated 29 new gut metagenomes from nine myrmecophagous species to reconstruct more than 300 bacterial genomes in which we identified chitin-degrading enzymes. Studying the distribution of these chitinolytic bacteria among hosts revealed both shared and specific bacteria between ant-eating species. Overall, our results highlight the potential role of gut symbionts in the convergent dietary adaptation of myrmecophagous mammals and the evolutionary mechanisms shaping their gut microbiota.

Effective combination of arugula vermicompost, chitin and inhibitory bacteria for suppression of the root-knot nematode Meloidogyne javanica and explanation of their beneficial properties based on microbial analysis.

Root-knot nematodes (Meloidogyne spp.) are dangerous parasites of many crops worldwide. The threat of chemical nematicides has led to increasing interest in studying the inhibitory effects of organic amendments and bacteria on plant-parasitic nematodes, but their combination has been less studied. One laboratory and four glasshouse experiments were conducted to study the effect on M. javanica of animal manure, common vermicompost, shrimp shells, chitosan, compost and vermicompost from castor bean, chinaberry and arugula, and the combination of arugula vermicompost with some bacteria, isolated from vermicompost or earthworms. The extract of arugula compost and vermicompost, common vermicompost and composts from castor bean and chinaberry reduced nematode egg hatch by 12-32% and caused 13-40% mortality of second-stage juveniles in vitro. Soil amendments with the combination vermicompost of arugula + Pseudomonas. resinovorans + Sphingobacterium daejeonense + chitosan significantly increased the yield of infected tomato plants and reduced nematode reproduction factor by 63.1-76.6%. Comparison of chemical properties showed that arugula vermicompost had lower pH, EC, and C/N ratio than arugula compost. Metagenomics analysis showed that Bacillus, Geodermatophilus, Thermomonas, Lewinella, Pseudolabrys and Erythrobacter were the major bacterial genera in the vermicompost of arugula. Metagenomics analysis confirmed the presence of chitinolytic, detoxifying and PGPR bacteria in the vermicompost of arugula. The combination of arugula vermicompost + chitosan + P. resinovorans + S. daejeonense could be an environmentally friendly approach to control M. javanica.

The Ability of Chitinolytic Bacteria to Control Colletotrichum capsici in Chili Plants

Anthracnose disease caused by Colletotrichum capsici is one of the important diseases in chili plants that can reduce yields up to 50-100%. Chitinolytic bacteria Bacillus thuringiensis AGBE 3.3.BB, B. cereus SLBE1.1. SN and B. toyonensis AGBE1.2.TL were antagonistic to C. capsici. This study aimed to determine the potential of chitinolytic bacteria in controlling C. capsici in chili plants. Three bacterial isolates were formulated using bran as a carrier medium. The research was divided into four stages: antagonist test, viability test, ability test of biological agents to control C. capsici and plant growth. This study showed that the severity of anthracnose in the bacterial formulation of B. thuringiensis strain AGBE 3.3 BB was lower, which was 64.3% compared to the control. Tests showed that the formulation of B. cereus SLBE1.1. SN, formulation B. toyonensis strain AGBE1.2TL, formulation B. thuringiensis strain AGBE 3.3 BB, and the consortium formulation could inhibit C. capsici infection. These results indicate that chitinolytic bacteria’s formulation has the potential to be a biological control agent against C. capsici.