Dynamic Analysis of an Algae-Bacteria Ecological Model

In the paper, under the framework of exploring the interaction between algae and bacteria, an algae-bacteria ecological model was established to analyze the interaction mechanism and growth coexistence mode between algicidal bacteria and algae. Firstly, mathematical work mainly provided some threshold conditions to ensure the occurrence of transcritical bifurcation and saddle-node bifurcation, which could provide certain theoretical support for selecting key ecological environmental factors and numerical simulations. Secondly, the numerical simulation work dynamically displayed the evolution process of the bifurcation dynamic behavior of the model (2.1) and the growth coexistence mode of algae and algicidal bacteria. Finally, it was worth summarizing that intrinsic growth rate and combined capture effort of algae population had a strong influence on the dynamic behavior of the model (2.1). Furthermore, it must also be noted that transcritical bifurcation and saddle-node bifurcation were the inherent driving forces behind the formation of steady-state growth coexistence mode between algicidal bacteria and algae. In summary, it was hoped that the results of this study would contribute to accelerating the study of the interaction mechanism between algicidal bacteria and algae.

Dynamics and diversity of symbiotic bacteria in Apolygus lucorum at different developmental stages

Background Apolygus lucorum is a worldwide omnivorous pest damaging a range of crops and causing great economic losses.Symbiotic bacteria living in insects play a key role in the nutrition,physiology,and behavior of hosts.Here,we present an experiment using Illumina HiSeq sequencing targeting the V3–V4 regions of bacteria’s 16S rRNA throughout the entire life cycle of A.lucorum.Results The first and second instar nymphs have the largest alpha diversity compared with other life stages of the insect.Bacterial phyla Proteobacteria(72.29%),Firmicutes(15.24%),Actinobacteria(7.76%)exhibit the largest relative abundance in all developmental stages.Erwinia(23.97%)and Lactococcus(10.62%)are the two genera with the high-est relative abundance.The relative abundance of Erwinia in the nymph stage is significantly greater than the adult stage,and the relative abundance of Lactococcus in 6-day-old and 9-day-old adult females is higher compared with adult males.Conclusions These results reveal that microbial community composition and relative abundance shift dynamically at different life stages,implying that different bacterial phyla and genera may have specific roles in specific life stages such as metabolism,nutrition absorption,detoxification,and reproduction.This study reveals for the first time the community composition and ecological dynamics of symbiotic bacteria throughout the life stages of A.lucorum,and thus may provide insight to new strategies for pest control.

Biodiversity of the Symbiotic Bacteria Associated with Toxic Marine Dinoflagellate Alexandrium tamarense

Paralytic shellfish poisoning (PSP) toxins are potent neurotoxins mainly produced by dinoflagellates and being concentrated in bivalves through food web transfer. Increasing number of findings of toxin-producing bacteria in the cells of dinoflagellate such as Alexandriumtamarense supports the hypothesis of the bacterial origin of PSP toxins. Evidence that there are specific symbiosis bacterial taxa associated with the phytoplankton indicates the presence of specific selective mechanisms between them, and implies that the symbiosis bacteria have some vital function to the benefit of the dinoflagellates. Studies on the role of toxin-producing symbiosis bacteria in the marine ecosystem are considered to be becoming more important. Although toxigenic bacteria could be isolated from toxic dinoflagellates, it was not clearly proven whether the isolated bacterial strains based on culture-dependent manner and the corresponding intracellular bacteria were the same because of microbial unculturability. This paper aims to demonstrate the biodiversity of the symbiotic bacteria associated with toxic dinoflagellate A. tamarense using the culture-indepen- dent high-throughput pyrosequencing method, as well as the phylogenetic analysis based on 16S rDNA sequences of the symbiotic cultivable bacteria strains isolated from toxic Alexander tamarense.

Diversity of symbiotic algae of the genus Symbiodinium in scleractinian corals of the Xisha Islands in the South China Sea

Symbiotic algae （Symbiodinium sp.） in scleractinian corals are important in understanding how coral reefs will respond to global climate change. The present paper reports on the diversity of Symbiodinium sp. in 48 scleractinian coral species from 25 genera and 10 families sampled from the Xisha Islands in the South China Sea, which were identified with the use of restriction fragment length polymorphism （RFLP） of the nuclear ribosomal DNA large subunit gene （rDNA）. The results showed that： （i） Symbiodinium Clade C was the dominant zooxanthellae in scleractinian corals in the Xisha Islands; （ii） Symbiodinium Clade D was found in the corals Montipora aequituberculata, Galaxea fascicularis, and Plerogyra sinuosa; and （iii） both Symbiodinium Clades C and D were found simultaneously in Montipora digitata, Psammocora contigua, and Galaxeafascicularis. A poor capacity for symbiosis polymorphism, as uncovered by RFLP, in the Xisha Islands indicates that the scleractinian corals have low adaptability to environmental changes. Further studies are needed to investigate zooxanthellae diversity using other molecular markers.

Dose and time response of ruminally infused algae on rumen fermentation characteristics,biohydrogenation and Butyrivibrio group bacteria in goats

Background： Micro-algae could inhibit the complete rumen BH of dietary 18-carbon unsaturated fatty acid （UFAs）. This study aimed to examine dose and time responses of algae supplementation on rumen fermentation, biohydrogenation and Butyrivibrio group bacteria in goats. Methods： Six goats were used in a repeated 3 x 3 Latin square design, and offered a fixed diet. Algae were infused through rumen cannule with 0 （Control）, 6.1 （L-AIg）, or 18.3 g （H-AIg） per day. Rumen contents were sampled on d 0, 3, 7, 14 and 20. Results： H-AIg reduced total volatile fatty acid concentration and acetate molar proportion （P 〈 0.05）, and increased propionate molar proportion （P 〈 0.05）, whereas L-AIg had no effect on rumen fermentation. Changes in proportions of acetate and propionate in H-AIg were obvious from d 7 onwards and reached the largest differences with the control on d 14. Algae induced a dose-dependent decrease in 18：0 and increased trons-18：1 in the ruminal content （P 〈 0.05）. H-AIg increased the concentrations of t9, t] 1-18：2 and tl 1, cl 5-18：2 （P 〈 0.05）. L-AIg only seemed to induce a transient change in 18-carbon isomers, while H-AIg induced a rapid elevation, already obvious on d 3, concentrations of these fatty acid rose in some cases again on d 20. Algae had no effect on the abundances of Butyrivibfio spp. and Butyrivibrio proteoclosdcus （P 〉 0.10）, while H-AIg reduced the total bacteria abundance （P 〈 0.05）. However, this was induced by a significant difference between control and H-AIg on d 14 （-4.43 %）. Afterwards, both treatments did not differ as increased variation in the H-AIg repetitions, with in some cases a return of the bacterial abundance to the basal level （d 0）. Conclusions： Changes in rumen fermentation and 18-carbon UFAs metabolism in response to algae were related to the supplementation level, but there was no evidence of shift in ruminal biohydrogenation pathways towards t1 0-18：1 L-AIg mainly induced a transient effect on rumen biohydrogenation of 18-carbon UFAs, while H-AIg showed an acute inhibition and these effects were not associated with the known hydrogenating bacteria.

<i>In Vitro</i>Antibacterial Activity of Flavonoid Extracts of Two Selected Libyan Algae against Multi-Drug Resistant Bacteria Isolated from Food Products

This study aimed to evaluate the antibacterial activity of flavonoids extracted from two Libyan brown algae namely Cystoseira compressa and Padina pavonica using microwave-assisted extraction method against pathogenic bacteria isolated from meat, meat products, milk and dairy products (Staphylococcus aureus subsp. aureus (5 isolates), Bacillus cereus (3 isolates), Bacillus pumilus (1 isolate), Salmonella enterica subsp. enteric (4 isolates) and Enterohaemor-rhagic Escherichia coli O157 (EHEC O157) (4 isolates)). All of these isolates were muti-drug resistant with high MAR index. The results showed that C. compressa extract exhibited better and stronger antibacterial activities against the seventeen tested isolates with inhibition zones diameter ranged from 14 - 22 mm compared to P. pavonica extract which showed positive effect against 9 isolates with low inhibition zone ranged from 11 - 16.5 mm. Flavonoids extracted from C. compressa also displayed the best spectrum of bactericidal effect with a ratio MBC/MIC ≤ 4 obtained on all susceptible tested bacterial strains. Flavonoids and proanthocyanidins significantly contributed to the antibacterial properties. The mode of action of these active extracts is under investigation.

Isolation and algae-lysing characteristics of the algicidal bacterium B5

Water blooms have become a worldwide environmental problem. Recently, algicidal bacteria have attracted wide attention as possible agents for inhibiting algal water blooms. In this study, one strain of algicidal bacterium B5 was isolated from activated sludge. On the basis of analysis of its physiological characteristics and 16S rDNA gene sequence, it was identified as Bacillusfusiformis. Its algaelysing characteristics on Microcystis aeruginosa, Chlorella and Scenedesmus were tested. The results showed that： （1） the algicidal bacterium B5 is a Gram-negative bacterium. The 16S rDNA nucleotide sequence homology of strain B5 with 2 strains of B. fusiformis reached 99.86%, so B5 was identified as B. fusiformis; （2） the algal-lysing effects of the algicidal bacterium B5 on M. aeruginosa, Chlorella and Scenedesrnus were pronounced. The initial bacterial and algal cell densities strongly influence the removal rates of chlorophyll-a. The greater the initial bacterial cell density, the faster the degradation of chlorophyll-a. The greater the initial algal cell density, the slower the degradation of chlorophyll-a. When the bacterial cell density was 3.6 × 10^7 cells/ml, nearly 90% of chlorophyll-a was removed. When the chlorophyll-a concentration was less than 550 μg/L, about 70% was removed; （3） the strain B5 lysed algae by secreting metabolites and these metabolites could bear heat treatment.

Isolation and identification of bacteria associated with the surfaces of several algal species

We conducted this study to assess the diversity of bacteria associated with the surfaces of algae based on 16S rDNA sequence analyses.Twelve strains of bacteria were obtained from the surfaces of the following four species of algae:Gracilaria textorii,Ulva pertusa,Laminaria japonica,and Polysiphonia urceolata.The isolated strains of bacteria can be divided into two groups:Halomonas and Vibrio,in physiology,biochemical characteristics and 16S rDNA sequence analyses.The phylogenetic tree constructed based on 16S rDNA sequences of the isolates shows four obvious clusters,Halomonas venusta,Vibrio tasmaniensis,Vibrio lentus,and Vibrio splendidus.Isolates from the surface of P.urceolata are more abundant and diverse,of which strains P9 and P28 have a 16S rDNA sequence very similar(97.5%-99.8%) to that of V.splendidus.On the contrary,the isolates from the surfaces of G.textorii,U.pertusa and L.japonica are quite simple and distribute on different branches of the phylogenetic tree.In overall,the results of this study indicate that the genetic relationships among the isolates are quite close and display a certain level of host species specificity,and alga-associated bacteria species are algal species specific.

Lytic Characteristics and Identification of Two Alga-lysing Bacterial Strains

All previously reported bacterial species which are capable of lysing harmful algae have been isolated from coastal environments in which harmful algae blooms have occurred. Due to the low concentration of alga-lysing bacteria in an algal bloom, it is difficult to isolate the alga-lysing bacteria by existing methods. In this paper, two algae-lysing bacterial strains, P01 and P03, have been isolated from a biosystem immobilized on a sponge that was highly effective in removing algae and microcystins. Their lysing modes and effects on Microcystis aeruginosa have been studied. The results show that the degradation processes of these two strains for M. aeruginosa accorded with a first-order reaction model when the chlorophylla concentration was in the range from 0 to 1000 μgL-1. The degradation rate constants were 0.1067, 0.1274 and 0.2792 for P01 and0.0683, 0.0744 and 0.028 97 for P03, when the bacterial densities were 8.6 × 105, 8.6 × 106 and 8.6 × 107cells mL-1 respectively. Moreover, the two bacterial strains had favourable lytic effects not only on M. aeruginosa , but also on Chlorella and Scene-desmus. Their lytic effect on M. aeruginosa did not require physical cell to cell contact, but proceeded by the production of an extracellular product. The bacterial strains were identified as Bacillus species by PCR amplification of the 16S rRNA gene, BLAST analysis, and comparison with sequences in the GenBank nucleotide database.

Changes of Cellular Superficial Configuration of Symbiotic Algae During Cultivation from Two Anemones Found in the South China Sea

Symbiotic algae from two anemones, Radianthus macrodactylus and Stichodactyla mertensii, found in the South China Sea, were cultivated in ASP-8A medium in this study. Changes of superficial configuration of symbiotic algae during the cultivation were studied by means of a microscope and a scanning electron microscope (SEM). A number of small cavities appeared on the sur- faces of symbiotic algae after they were cultivated for 10 h. The cavities enlarged and the cell contents were lost with extended culti- vation. Our data suggested that the presence of cavities on symbiotic algae surfaces may be one of the main reasons for failure to culture symbiotic algae in an artificial medium.

The impact of allelochemicals on the differential expression of symbiotic bacteria in cotton aphids

Insects have developed a good adaptive mechanism in response to environmental stresses in the long-term evolution. They have developed a helpful metabolism system to resist plant allelochemicals. Insects also harbor different kinds of symbiotic bacteria, which provide them a competitive advantage. Here, using cotton aphid as an example, we investigated the effects of four plant allelochemicals on the differential expression of symbiotic bacteria based on transcriptome data. We also studied the composition of symbiotic bacteria and function on pathway level in three kinds of aphids. We found that the bacteria have a significant role in resisting the plant allelochemicals stress and host plant selection by aphids. These results should be useful to investigate the environmental adaption mechanism of aphids in the view of symbiotic bacteria. These results would offer a new insight for improving strategy of aphids and developing new pest control systems.

Metabolic relationships between marine red algae and algae‑associated bacteria

Mutualistic interactions between marine phototrophs and associated bacteria are an important strategy for their success-ful survival in the ocean,but little is known about their metabolic relationships.Here,bacterial communities in the algal sphere(AS)and bulk solution(BS)of nine marine red algal cultures were analyzed,and Roseibium and Phycisphaera were identified significantly more abundantly in AS than in BS.The metabolic features of Roseibium RMAR6-6(isolated and genome-sequenced),Phycisphaera MAG 12(obtained by metagenomic sequencing),and a marine red alga,Porphyridium purpureum CCMP1328(from GenBank),were analyzed bioinformatically.RMAR6-6 has the genetic capability to fix nitrogen and produce B vitamins(B1,B2,B5,B6,B9,and B12),bacterioferritin,dimethylsulfoniopropionate(DMSP),and phenylacetate that may enhance algal growth,whereas MAG 12 may have a limited metabolic capability,not producing vitamins B9 and B12,DMSP,phenylacetate,and siderophores,but with the ability to produce bacitracin,possibly modulating algal microbiome.P.purpureum CCMP1328 lacks the genetic capability to fix nitrogen and produce vitamin B12,DMSP,phenylacetate,and siderophore.It was shown that the nitrogen-fixing ability of RMAR6-6 promoted the growth of P.pur-pureum,and DMSP reduced the oxidative stress of P.purpureum.The metabolic interactions between strain RMAR6-6 and P.purpureum CCMP1328 were also investigated by the transcriptomic analyses of their monoculture and co-culture.Taken together,potential metabolic relationships between Roseibium and P.purpureum were proposed.This study provides a bet-ter understanding of the metabolic relationships between marine algae and algae-associated bacteria for successful growth.

Isolation and Characterization of an Algicidal Bacterium Indigenous to Lake Taihu with a Red Pigment able to Lyse Microcystis aeruginosa

Objective To isolate and characterize indigenous algicidal bacteria and their algae-lysing compounds active against Microcystis aeruginosa, strains TH1, TH2, and FACHB 905. Methods The bacteria were identified using the Biolog automated microbial identification system and 16S rDNA sequence analysis. The algae-lysing compounds were isolated and purified by silica gel column chromatography and reverse-phase high performance liquid chromatography. Their structures were confirmed by Nuclear Magnetic Resonance （NMR） and Fourier Transform infrared （FT-IR） spectroscopy. Algae-lysing activity was observed using microscopy. Results The algae-lysing bacterium LTH-2 isolated from Lake Taihu was identified as Serratia marcescens. Strain LTH-2 secreted a red pigment identified as prodigiosin （C20H25N30）, which showed strong lytic activity with algal strains M. aeruginoso TH1, TH2, and FACHB 905 in a concentration-dependent manner. The 50% inhibitory concentration （ICs0） of prodigiosin with the algal strains was 4.8 （±0.4）×10^-2 μg/mL, 8.9 （±1.1）×10^-2μg/mL, and 1.7 （±0.1）×10^-1 μg/mL in 24 h, respectively. Conclusion The bacterium LTH-2 and its pigment related to damage of cell membranes. The bacterium for regulating blooms of harmful M. aeruginosa. had strong Microcystis-lysing activity probably LTH-2 and its red pigment are potentially useful

冰封期不同类型湖泊细菌与蓝藻群落组成及共现网络分析

季节性冰封使得寒区湖泊微生物群落结构及生物间的相互反馈具有特殊性。黄河流域内蒙古段湖泊作为典型的寒区湖泊,其漫长的冰封期为研究细菌与蓝藻在冰封条件下的相互关系提供了天然平台。解析不同类型湖泊生态系统中细菌与蓝藻群落间的相互关系差异,有助于深入理解湖泊冰封条件下水生态系统的功能与动态。为探明湖泊功能对菌藻关系的影响,本文以大型淡水湖泊乌梁素海、城市湖泊南海湖、咸水湖泊岱海冰封期冰下水体为研究对象,利用宏基因测序分子生物学技术、冗余分析、Mantel检验分析及Network网络分析模型等方法,对冰封期间细菌和蓝藻群落结构及相互关系进行研究。结果表明:3个湖泊冰下水体中优势菌门组成一致,属水平上的群落组成具有较为明显的差异;湖泊间菌藻群落组成差异与环境因子的协同作用高度相关,总磷、氨氮和总氮是影响冰封期菌藻群落结构的主要环境因子;细菌-蓝藻的微生物网络复杂性呈现南海湖>岱海>乌梁素海。岱海网络中菌藻关系多以负相关为主,负权重边占比达到31.70%,且模块化程度较高。本文旨在对湖泊冰下水体中的细菌、蓝藻群落结构及共现网络进行深入分析,以更好地理解不同水生态系统下微生物错综复杂的关系,为相关领域的生态保护和研究提供重要的理论依据。

昆虫源共生菌鉴定方法研究进展

昆虫与共生菌的互利共生关系对于维持昆虫正常的生理功能和行为具有关键作用。研究共生菌对于理解昆虫生态、提高农业生产效率以及开发新的生物制药方法具有重要意义。然而,共生菌的多样性及其复杂的生态环境,对其鉴定提出了挑战。本研究回顾了从传统培养方法到先进分子生物技术的发展,特别关注了基于16S r RNA基因的分子鉴定、分子生物学方法和高通量测序技术在昆虫源共生菌鉴定中的应用,旨在为深入了解该领域提供资源。

Blooming of bacteria and algae is a biokiller for mass-extinction of Devonian coral-stromatoporoid reef ecosystems

Studies of rock slices showed that there were many kinds of symbioses between bacteria and algae and corals-stromatoporoids in the coral-stromatoporoid reefs from the Devonian Ganxi section of Sichuan and the Dushan section of Guizhou in South China. They included encrustations, microborings, bioclaustration, etc. In the host corals-stromatoporoids invaded by bacteria and algae were many residues of dead soft issue in the infected parts, where the skeletal structures were injured. Therefore, we considered there were direct interactions between corals-stromatoporoids and bacteria and algae in coral-stromatoporoid reefs, which included that bacteria and algae blocked growth of corals-stromatoporoids and the latter had the ability of self-healing. And the bacteria and algae usually was the active side. In the Middle Devonian with normal seawater condition, corals and stromatoporoids had the ability to resist the invasion of bacteria and algae, and the host coral-stromatoporoids would not be killed; but in the Late Devonian with deterioration of seawater quality, the ability of bacteria and algae infection increased while corals-stromatoporoids' ability to resist infection declined, and therefore the host corals-stromatoporoids would be dead. Hence we suggested that the invading of bacteria and algae was a possible biokiller for mass-extinction of the Devonian coral-stromatoporoid reefs ecosystem. Beyond that, blooming of bacteria and algae and its triggering cumulative environmental effects played an important role in the reduction and extinction of metazoan in the Late Devonian. Furthermore, it can be used as a useful example to learn the trend and the reasons for the disease and decrease of modern coral reefs.

褐飞虱和白背飞虱混合饲养中的共生细菌转移

【目的】探究褐飞虱Nilaparvata lugens和白背飞虱Sogatella furcifera的种间互作是否会导致其共生细菌的变化。【方法】分别对褐飞虱和白背飞虱进行单独饲养或混合饲养,并基于16S rRNA基因测序,分析不同饲养褐飞虱和白背飞虱种群共生细菌的多样性。【结果】混合饲养的与单独饲养的相比,褐飞虱和白背飞虱的共生菌群落结构均发生明显变化且具有趋同现象;混合饲养的褐飞虱共生细菌多样性比单独饲养的显著增加;褐飞虱中的133个扩增子序列变异(amplicon sequence variants,ASVs)和白背飞虱中的143个ASVs被定义为潜在的水平转移物种。【结论】褐飞虱和白背飞虱的种间互作改变了其共生细菌群落,研究结果为深入研究基于共生细菌的稻飞虱种间互作提供了新视角。

不同碳源下共存细菌对铜绿微囊藻生长的影响

铜绿微囊藻(Microcystis aeruginosa)可通过二氧化碳浓缩机制(carbon concentrating mechanism,CCM)利用水环境中的无机碳进行光合固碳来促进自身生长,是引发淡水蓝藻水华的优势种。自然水体生态系统中菌藻共生体系是其重要组成部分,对藻华起到重要调控作用,但有关不同碳源条件下共生细菌对蓝藻藻华的影响仍不清楚。文章以铜绿微囊藻为模式蓝藻,探究在不同碳源组合下共存细菌对其生长的影响。在总碳(total carbon,TC)质量浓度为25 mg/L的无机碳源和有机碳源组合,环境初始菌藻比为1∶2时,铜绿微囊藻的最大生物量达到最大值5.0×10^(7)个/mL,是纯藻对照组最大生物量的2.05倍;在加入25 mg/L的有机碳源,初始菌藻比为5∶1时,培养周期内可预测的最大生物量达到最小,为1.5×10^(7)个/mL,仅为纯藻对照组最大生物量的0.76倍。结果表明:不同碳源下初始细菌的出现会极大程度地影响铜绿微囊藻的生长,其中,在无机碳源和混合碳源的营养条件下,初始细菌显著加快了铜绿微囊藻的生长繁殖。