Selecting Bacterial Strains for Use in the Biocontrol of Diseases Caused by <Emphasis Type="Italic">Phytophthora capsici</Emphasis> and <Emphasis Type="Italic">Alternaria alternata</Emphasis> in Sweet Pepper Plants

More than 500 isolates of bacteria were obtained from the aerial part and rhizosphere of sweet pepper (Capsicum annuum L.) plants harvested from different places in the Region of Murcia (Spain). The isolates were purified and assayed in vitro against Phytophthora capsici and Alternaria alternata. Sixty isolates (12 %) produced an inhibition zone against at least one of the pathogens, while ten had a strongly inhibitory effect on both pathogens assayed. Microscopic observation of interactions zone showed cell vacuolisation, hyphae lysis and spilling of cytoplasm content of the pathogens in the culture media. These ten isolates were then chosen for biocontrol of Phytophthora root rot and Alternaria leaf spots of pepper plants in vivo. Four of them denominated HS93, LS234, LS523 and LS674 reduced P. capsici root rot by 80, 51, 49 and 54 %, respectively, and A. alternata leaf spots by 54, 74, 62 and 53 %. HS93 belongs to the genus Bacillus and probably the species subtilis, while LS234, LS523 and LS674 belong to the genus Bacillus and probably the species licheniformis. Dry mass of plants treated with these bacteria was significantly higher than that of non-treated and inoculated plants.     

How to identify and quantify the members of the Bacillus genus?

Members of the Bacillus genus are widely distributed throughout natural environments and have been studied for decades among others for their physiology, genetics, ecological functions, and applications. However, despite its prevalence in nature, the characterization and classification of Bacillus remain challenging due to its complex and ever-evolving taxonomic framework. This review addresses the current state of the Bacillus taxonomic landscape and summarizes the critical points in the development of Bacillus phylogeny. With a clear view of Bacillus phylogeny as a foundation, we subsequently review the methodologies applied in identifying and quantifying Bacillus, while also discussing their respective advantages and disadvantages.     

Identification and Growth Characteristics of α-Galactosidase-producing Microorganisms

Two kinds of α-galactosidase-producing microorganisms, strain No. 31–2 and strain No. 7–5, have been isolated from soil and subjected to a determinative study. On the basis of the morphological and physiological characters, the strain No. 31–2 was identified to be belonged to genus Micrococcus and the strain No. 7–5 to genus Bacillus. The former strain, Micrococcus sp. No. 31–2, produced exclusively an intracellular α-galactosidase, and the latter one, Bacillus sp. No. 7–5, secreted the enzyme into culture medium. The cell growth and enzyme production of both strains were observed to reach the maximum under an alkaline culture condition. The intracellular α-galactosidase of Micrococcus sp. No. 31–2 was inducible by galactose, melibiose, and raffinose, while the α-galactosidase of Bacillus sp. No. 7–5 was produced constitutively.     

Prevalence and expression of enterotoxins in Bacillus cereus and other Bacillus spp., a literature review

Members of the Bacillus genus are ubiquitous soil microorganisms and are generally considered harmless contaminants. However, a few species are known toxin producers, including the foodborne pathogen, B. cereus. This species produces two distinct types of foodborne illness, the emetic (vomit-inducing) syndrome, associated with consumption of toxin in cooked rice dishes, and the diarrheal illness seen occasionally following consumption of contaminated meats, sauces, and certain dairy products. In the latter case, illness results from the production of enterotoxins by vegetative cells in the small intestine of the host. In dairy products, the occurrence of Bacillus spp. is inevitable, and the spore-forming ability of this organism allows it to easily survive pasteurization. Many strains have been shown to grow and produce enterotoxin in dairy products at refrigeration temperatures. Evaluation of toxin gene presence and toxin expression in Bacillus spp. other than B. cereus has not been thoroughly investigated. However, the presence of natural isolates of Bacillus spp. harboring one or more enterotoxin gene(s) and subsequent demonstration of conditions which may support toxin expression holds crucial importance in the food safety arena.     

Bacillus-based bionematicides: development,modes of action and commercialisation

Agricultural crops are severely damaged by root-knot nematodes causing extensive financial losses globally. Historically, agrochemicals have been the preferred method to combat these pests; however, threats to humans and the environment posed by these agrochemicals led to the need for developing new biocontrol agents. Importantly, the latter should adhere to biosafety regulations while being highly effective. Root-knot nematodes live in soil and thus the use of rhizobacteria such as Bacillus for biocontrol development have shown potential. Although various Bacillus species have been tested in this capacity, little is known about their secondary metabolites and the mechanisms of action responsible for their nematicidal activity. If these secondary metabolites can be qualitatively and quantitatively characterised, metabolic features could be synthetically engineered and used to combat root-knot nematodes. Although there is great potential for bionematicides, the commercialisation and development of such products can be difficult. This review summarises the importance of Bacillus species as natural antagonists of root-knot nematodes through the production of secondary metabolites. It provides an overview of the significance of root-knot nematodes in agriculture and the advances of chemical nematicides in recent years. The potential of Bacillus species as biocontrol agents, the known mechanisms of action responsible for the nematicidal activity demonstrated by Bacillus species, non-target effects of biocontrol agents and the commercialisation of Bacillus-based bionematicides are discussed.     

Ecology and biotechnological potential of <Emphasis Type="Italic">Paenibacillus polymyxa</Emphasis>: a minireview

Microbial diversity is a major resource for biotechnological products and processes. Bacteria are the most dominant group of this diversity which produce a wide range of products of industrial significance. Paenibacillus polymyxa (formerly Bacillus polymyxa), a non pathogenic and endospore-forming Bacillus, is one of the most industrially significant facultative anaerobic bacterium. It occurs naturally in soil, rhizosphere and roots of crop plants and in marine sediments. During the last two decades, there has been a growing interest for their ecological and biotechnological importance, despite their limited genomic information. P. polymyxa has a wide range of properties, including nitrogen fixation, plant growth promotion, soil phosphorus solubilisation and production of exopolysaccharides, hydrolytic enzymes, antibiotics, cytokinin. It also helps in bioflocculation and in the enhancement of soil porosity. In addition, it is known to produce optically active 2,3-butanediol (BDL), a potentially valuable chemical compound from a variety of carbohydrates. The present review article aims to provide an overview of the various roles that these microorganisms play in the environment and their biotechnological potential.     

Optimization of physical factors affecting the production of thermo-stable organic solvent-tolerant protease from a newly isolated halo tolerant Bacillus subtilis strain Rand

Background  

Many researchers have reported on the optimization of protease production; nevertheless, only a few have reported on the optimization of the production of organic solvent-tolerant proteases. Ironically, none has reported on thermostable organic solvent-tolerant protease to date. The aim of this study was to isolate the thermostable organic solvent-tolerant protease and identify the culture conditions which support its production. The bacteria of genus Bacillus are active producers of extra-cellular proteases, and the thermostability of enzyme production by Bacillus species has been well-studied by a number of researchers. In the present study, the Bacillus subtilis strain Rand was isolated from the contaminated soil found in Port Dickson, Malaysia.     

缓解花生连作障碍的根际促生菌分离及功能鉴定

【目的】长期连作障碍严重降低花生生产的产量及品质,根际促生菌可有效降解土壤中自毒化感物质、抑制植物病原菌生长及促进植物生长,从而有效缓解连作障碍问题。筛选优化具有缓解花生连作障碍能力的多功能根际益生微生物,验证其益生作用能力,为根际促生菌株在连作障碍中的应用提供理论依据及技术支持。【方法】采集连作12年地块花生根际土壤,利用以酚酸为唯一碳源的筛选培养基获得具有酚酸自毒化感物质降解及利用能力的根际促生菌,通过16S rRNA基因测序进行系统发育分析,确定根际促生菌菌株的分类地位,并验证其对植物病原菌生长抑制能力及解磷、解钾、产植物激素吲哚乙酸能力。【结果】从连作12年的花生发病土壤中获得7株可高效降解酚酸类自毒物质且降解底物多样的根际微生物菌株,经16S rRNA测序比对分别为克雷伯氏菌B02 (Klebsiella sp. B02)、克雷伯氏菌B07(Klebsiella sp. B07)、克雷伯氏菌B15 (Klebsiella sp. B15)、芽孢杆菌B28 (Bacillus sp. B28)、不动杆菌P09(Acinetobacter sp. P09)、布鲁氏杆菌VA05 (...     

Multiple reproductive strategies of a spring ephemeral plant,Fritillaria maximowiczii,enable its adaptation to harsh environments

Spring ephemeral plants that experience harsh environments have developed specific reproductive characteristics. These characteristics are of great importance to the survival and reproduction of these species, particularly for rare and endangered plants. Fritillaria is a genus consisting of spring ephemeral plants with significant medicinal and ornamental value whose wild resources are highly threatened and whose reproductive characteristics and adaptative evolutionary mechanisms are still not well understood. Fritillaria maximowiczii is positioned at the most basal clade on the Fritillaria phylogenetic tree, whose reproductive characteristics remain obscure. In this study, we report the flowering dynamics, pollination biology and breeding system of F. maximowiczii. The flowering process of F. maximowiczii can be divided into seven stages. Based on the pollen/ovule ratio, the outcrossing index and a field pollination experiment on a natural population, F. maximowiczii showed high levels of outcrossing and self-compatibility. Three types of pollinators were observed: two kinds of bumblebees, and spiders. Diverse herkogamy and dichogamy may have considerably improved its reproductive success rate. Furthermore, a special reproductive mode not previously reported in wild populations of Fritillaria, apomixis, was strongly suspected based on a high fruit setting rate (36.84%). Our study suggests F. maximowiczii has developed multiple reproductive strategies to adapt to harsh environments and ensure population reproduction, and the diverse reproductive mechanisms may be related to its primitive phylogenetic position in the genus. This study not only broadens our understanding of mechanisms of ecological adaptation in spring ephemeral plants but also provides key data for the conservation of Fritillaria.     

Artificial wind-gust liberation of microbial bioaerosols previously deposited on plants

Summary A bioaerosol research chamber was constructed and used to evaluate wind-gust release of previously depositedPseudomonas syringae, spores ofBacillus subtilis var.niger, and fluorescent microspheres (FM) on oat plants, and the airborne survival of the releasedP. syringae. Observations of wind gusts on the releasedBacillus spores and FM showed they had similar particle size distributions and therefore FM could act as bacterial sized surrogates in particle dispersion. Microscopic examination of the released FM containing particles revealed that 84% were associated with either fungal spores and hyphae were epiphytic on the plant, or with plant and soil debris. The release rate ofBacillus spores decreased as the number of gusts experienced by the plants increased, with a greater proportion of larger particles removed. The larger the particle associated with the releasedP. syringae, the longer the bacteria survived.     

Application of Bacillus species in the control of root rot diseases of crop plants

Bio control potential of three Bacillus spp viz., Bacillus subtilis, B. thuringiensis and B. cereus, against soil borne root-infecting fungi on cowpea and mash bean plants were tested both in vitro and in vivo. All three species showed efficiency and produced nodules on mash bean and cow pea plants. In vitro dual culture plate method showed significant inhibition of Fusarium spp. by all these three species of Bacillus with the appearance of a prominent zone of inhibition while a maximum zone of inhibition of Fusarium spp. was observed by B. thuringiensis, whereas in case of Macrophomina phaseolina and Rhizoctonia solani, the highest zone of inhibition was observed by B. subtilis. Bacillus spp. used as seed dressing and soil drenching showed a significant increase in shoot length, shoot weight, root length and root weight in cow pea and mash bean plants. Maximum shoot length was observed in cow pea plants where Bacillus spp. were drenched in soil, whereas maximum root length and root weight in cow pea was observed when B. thuringiensis used as seed dressing. Seed dressing and soil drenching with species of Bacillus viz., B. subtilis, B. thuringiensis and B. cereus, were found to be an effective method for the control of soil borne root-infecting fungi like M. phaseolina, R. solani and Fusarium spp., on cow pea and mash bean plants.     

Diazotrophic bacilli isolated from the sunflower rhizosphere and the potential of Bacillus mycoides B38V as biofertiliser

The nitrogen fixation by strains belonging to the Bacillus genus remains poorly explored. In this work, the diversity of endospore‐forming bacilli isolated from the rhizosphere of sunflower was evaluated. A total of 101 strains were identified based on the V1‐V2 variable regions of the 16S rRNA gene. Strains belonging to the genera Bacillus and Paenibacillus represented 41.6% and 58.4%, respectively, of total isolates. The production of indolic compounds was a common trait among the isolates, and approximately 75% of them exhibited positive nitrogenase activity; but only 9.2% displayed activities higher than 1 nmol C₂H₄ mg protein h^?1. Within the genus Bacillus, the isolates related to the B. cereus group displayed the highest nitrogenase activity and were the second most frequent group of Bacillus sp. isolated. Plants inoculated with the isolate B38V showed the highest N content, and their shoot dry weights were significantly increased compared with positive control. Our results indicated that B38V, which belongs to the B. mycoides species, has the potential to promote sunflower growth. The data obtained in this study provide additional information concerning the diversity of Gram‐positive diazotrophic within the genera Bacillus and Paenibacillus and their potential for the biofertilisation of sunflower crops.     

Phytochemical Constituents and Biological Activities of Plants from the Genus Cissampelos

Cissampelos is a significant genus comprising of approximately 21 species of the medicinal plants (Menispermaceae). The plants of this genus are used in traditional medicine for the treatment of various ailments such as asthma, arthritis, dysentery, hyperglycemia, cardiopathy, hypertension and other related problems. These plants are rich in bioactive dibenzylisoquinoline and aborphine as well as small amounts of other ingredients. In recent years, the chemical constituents and pharmacological activities of Cissampelos genus have been paid more and more attention due to their diversity. Herein, we compile the chemical constituents and biological activities on this genus, and summarize the ¹³C-NMR data of the main bioactive ingredients. All information comes from scientific databases such as Google Scholar, PubMed, Sci-Finder, ScienceDirect, Web of Science and CNKI. It provides valuable data for the future research and development of Cissampelos genus.     

Characterization of feather-degrading bacteria from Brazilian soils

Studies on keratinolytic microorganisms have been mainly related to their biotechnological applications and association with animal pathologies. However, these organisms have an ecological relevance to recycling keratinous residues in nature. This work aimed to select and identify new culturable feather-degrading bacteria isolated from soils of Brazilian Amazon forest and Atlantic forest. Bacteria that were isolated from temperate soils and bacteria from Amazonian basin soil were tested for their capability to grow on feather meal agar (FMA). Proteolytic bacteria were tested for feather degradation and were further identified according to their morphological and biochemical characteristics. Also, molecular identification based on 16S rDNA gene sequencing was carried out. A total of 24 proteolytic and 20 feather-degrading isolates were selected; Most of the isolates were from the Bacillus genus (division Firmicutes), but one Aeromonas, two Serratia (??-Proteobacteria), and one Chryseobacterium (Cytophaga-Flavobacterium group).     

Enhancement of the efficiency of Cd phytoextraction using bacterial endophytes isolated from Chromolaena odorata,a Cd hyperaccumulator

Phytoextraction is a technique using a hyperaccumulator to remove heavy metals from soil. The efficiency of heavy metal uptake can be enhanced by the inoculation of endophytes. In this study, we isolated and identified 23 endophytes from Chromolaena odorata, a cadmium (Cd) hyperaccumulator that consisted of 19 bacteria, 2 actinomycetes and 2 fungi. All bacteria and fungi could produce at least 1 plant growth promoting factors. However, only 4 bacterial isolates; Paenibacillus sp. SB12, Bacillus sp. SB31, Bacillus sp. LB51, and Alcaligenes sp. RB54 showed the highest minimum inhibitory concentration (MIC) value (2.9 mM), followed by Exiguobacterium sp.RB51 (1.7 mM). Then, these 5 high-MIC bacteria and 1 low-MIC bacterium, Bacillus sp. LB15 were inoculated onto sunflower grown in soil supplemented with 250 mg/kg of Cd. After 60 days, all inoculated plants accumulated significantly higher Cd concentration than the non-inoculated counterparts, and those inoculated with strain LB51 showed the highest Cd accumulation and growth. Interestingly, strain LB15 with low MIC also enhanced Cd accumulation in plants. The results suggest that these bacteria, particularly strain LB51, could be applied to improve Cd accumulation in plants, and that bacteria with low MIC also have the potential to enhance the efficiency of phytoextraction.     

Evolution of a non-flying mammal-dependent pollination system in Asian Mucuna (Fabaceae)

Pollinator shifts are often related to speciation in angiosperms, and the relationship between them has been discussed in several plant taxa. Although limited information on plants pollinated by non-flying mammals in Central and South America and Africa is available, related research has not been conducted in Asia. Herein, I summarize the available knowledge of pollination in Asian Mucuna (Fabaceae), a genus mainly distributed in the tropics, and discuss the evolution of plants pollinated by non-flying mammals in Asia. Nineteen pollinator species have been recorded and pollination systems have been categorized into four types. An examination of the relationship between Mucuna species and their pollinators from the lineage perspective revealed that all species in Mucuna, subgenus Macrocarpa, which are distributed in Asia, are pollinated exclusively by non-flying mammals. Additionally, plants pollinated by non-flying mammals were found to have diverged from bat-pollinated and non-flying mammal-pollinated plants, while plants pollinated by non-flying mammals have evolved multiple times. This is a unique example of evolutionary transition. I hypothesize that the diversification of squirrel species in tropical Asia may have led to the speciation and diversification of Mucuna in Asia. Furthermore, the behavioural and ecological characteristics of bats and birds in Asia differ from the characteristics of those in other regions, implying that Asian Mucuna species do not rely on bat or bird pollinators. The adaptation of floral characteristics to pollinators is not well understood in Asia. Mammal-pollinated plants in Asia may have evolved differently from those in other regions and have unique pollination systems.     

An overview of Bacillus proteases: from production to application

Proteases have a broad range of applications in industrial processes and products and are representative of most worldwide enzyme sales. The genus Bacillus is probably the most important bacterial source of proteases and is capable of producing high yields of neutral and alkaline proteolytic enzymes with remarkable properties, such as high stability towards extreme temperatures, pH, organic solvents, detergents and oxidizing compounds. Therefore, several strategies have been developed for the cost-effective production of Bacillus proteases, including optimization of the fermentation parameters. Moreover, there are many studies on the use of low-cost substrates for submerged and solid state fermentation. Other alternatives include genetic tools such as protein engineering in order to obtain more active and stable proteases and strain engineering to better secrete recombinant proteases from Bacillus through homologous and heterologous protein expression. There has been extensive research on proteases because of the broad number of applications for these enzymes, such as in detergent formulations for the removal of blood stains from fabrics, production of bioactive peptides, food processing, enantioselective reactions, and dehairing of skins. Moreover, many commercial proteases have been characterized and purified from different Bacillus species. Therefore, this review highlights the production, purification, characterization, and application of proteases from a number of Bacillus species.     

Enhanced growth of halophyte plants in biochar‐amended coastal soil: roles of nutrient availability and rhizosphere microbial modulation

Soil health is essential and irreplaceable for plant growth and global food production, which has been threatened by climate change and soil degradation. Degraded coastal soils are urgently required to reclaim using new sustainable technologies. Interest in applying biochar to improve soil health and promote crop yield has rapidly increased because of its multiple benefits. However, effects of biochar addition on the saline–sodic coastal soil health and halophyte growth were poorly understood. Response of two halophytes, Sesbania (Sesbania cannabina) and Seashore mallow (Kosteletzkya virginica), to the individual or co‐application of biochar and inorganic fertilizer into a coastal soil was investigated using a 52 d pot experiment. The biochar alone or co‐application stimulated the plant growth (germination, root development, and biomass), primarily attributed to the enhanced nutrient availability from the biochar‐improved soil health. Additionally, the promoted microbial activities and bacterial community shift towards the beneficial taxa (e.g. Pseudomonas and Bacillus) in the rhizosphere also contributed to the enhanced plant growth and biomass. Our findings showed the promising significance because biochar added at an optimal level (≤5%) could be a feasible option to reclaim the degraded coastal soil, enhance plant growth and production, and increase soil health and food security.     

先锋种丰富度对边坡植被群落特征及其护坡效益的影响

乡土植物灌木化建植是高速公路边坡防护的重要途径。以成渝高速(G85)永川段为例,以西南地区两种典型的边坡绿化初始配置"慈竹(Neosino calamus affinis)+野牛草(Buchloe dactyloides)"、"棉槐(Amorpha fruticosa)+紫羊茅(Festuca rubra)"为基础,分别与马棘(Indigofera pseudotinctoria Mats.)、黄荆(Vitex negundo)、狗牙根(Cynodon dactylon)、芒(Miscanthus sinensis)等路域优势种以不同方式组合,研究一定立地条件下初始绿化植物(先驱植物)的丰富度对边坡植被群落生长发育、早期演替行为及护坡性能的影响。结果表明:1)先驱植物丰富度可直接影响边坡植被的成坪时间、生物量积累:相同建植条件(边坡条件、播种密度等)下,先锋种种类越多,成坪时间就越短,被积累的生物量也越多;2)先锋种数量与群落的生物多样性水平有关(R20.954):相同演替阶段内,先锋种越多,群落的多样性水平(如物种丰富度、Shannon-Wiener指数、Pielou指数)则越高;3)群落中物种多样性水平与植被的护坡性能密切相关(R20.998):多样性水平越高,植被的蓄水、保土能力越强,边坡内径流系数、土壤侵蚀模数越小。可见,在边坡条件、播种密度等建植条件与建植措施一致的情形下,提高初始绿化植物的物种数可有效改善边坡植被的护坡性能。     

湖南南部植物区系新资料

本文报道了湖南双子叶植物1个新记录属、2个新记录种以及1个新记录变种,即中华青牛胆 ［Tinospora sinensis (Loureiro) Merrill］、柳叶润楠(Machilus salicina Hance)、广西白背叶(Mallotus apelta var. kwangsiensis F. P. Metcalf)、赛葵 ［Malvastrum coromandelianum (Linnaeus) Garcke］,赛葵对应的赛葵属(Malvastrum A. Gray)为湖南植物新记录属。入侵植物赛葵可能会对当地的农业生产和生态造成破坏。