Evidence of aerobic and anaerobic format dehydrogenase and aldehyde dehydrogenase immunological similarities shown by polyclonal antibodies raised against molybdoproteins

Antisera against metal(Mo)-containing dye-linked dehydrogenases from sulphate-reducing bacteria were used to screen for immunological similarities with NAD⁺-linked dehydrogenases detected in aerobic methanol-utilizing bacterial isolates. Out of eleven strains tested, the strains #5, 8, 9 and 11 were shown to have specific formate and aldehyde dehydrogenases displaying antibody cross-reaction against highly purified Mo-containing dye-linked dehydrogenases. The apparent molecular mass of the identified proteins observed during the antibody reaction correlated with the molecular mass of the dehydrogenases obtained after native PAGE electrophoresis. The strains #8 and 11 exhibited one formate dehydrogenase apparently of identical molecular mass 140–145 kDa, whereas strains #5, 9 and 11 synthesized aldehyde dehydrogenases with apparent molecular masses of about 110, 120 and 155 kDa (two forms) and 120 kDa, respectively. All these aerobic enzymes shared antigenic properties with the anaerobic metalloproteins, indicating the existence of structural similarities between those enzymes in spite of having different cofactor moieties.     

The use of fluorescent reporter protein tagging to study the interaction between Root‐Knot Nematodes and Soft Rot Enterobacteriaceae

The study of plant parasitic nematodes such as Meloidogyne spp. and their interactions with phytopathogenic bacteria remains underexplored. One of the challenges towards establishing such interactions is the dependence on symptom development as a measure of interaction. In this study, mCherry was employed as a reporter protein to investigate the interaction between the soft rot Enterobacteriaceae (SRE) Pectobacterium carotovorum subsp. brasiliensis (Pcb) and root‐knot nematode (M. incognita). Pectobacterium carotovorum subsp. brasiliensis was transformed with pMP7604 generating Pcb_mCherry strain. This strain was shown to attach to the surface coat of M.incognita J2 at the optimum temperature of 28°C. This suggests that RKN juveniles may play a role in disseminating Pcb in soils that are heavily infested with Pcb. The presence of RKN juveniles was shown to play a role in introducing Pcb_mCherry into potato tubers potentially acting as a source of latent tuber infections.

Significance and Impact of the Study

This study uses fluorescent reporter protein tagging as a tool to demonstrate the interaction between root‐knot nematode (Meloidogyne incognita) and the soft rot Enterobacteriacea (Pectobacterium carotovorum subsp. brasiliensis). Introduction of Pectobacterium through wounds generated by second‐stage juveniles (J2) into potato tubers was demonstrated. These results suggest that RKN juveniles can facilitate latent infection of potato tubers in the soil. These findings have important implications in the management of RKN and SRE in seed potato production. Furthermore, this tool can be used to study other nematode–bacteria interactions that have not been previously studied.     

FTIR Spectroscopic Study of Biogenic Mn-Oxide Formation by Pseudomonas putida GB-1

Biomineralization in heterogeneous aqueous systems results from a complex association between pre-existing surfaces, bacterial cells, extracellular biomacromolecules, and neoformed precipitates. Fourier transform infrared (FTIR) spectroscopy was used in several complementary sample introduction modes (attenuated total reflectance [ATR], diffuse reflectance [DRIFT], and transmission) to investigate the processes of cell adhesion, biofilm growth, and biological Mn-oxidation by Pseudomonas putida strain GB-1. Distinct differences in the adhesive properties of GB-1 were observed upon Mn oxidation. No adhesion to the ZnSe crystal surface was observed for planktonic GB-1 cells coated with biogenic MnO _x , whereas cell adhesion was extensive and a GB-1 biofilm was readily grown on ZnSe, CdTe, and Ge crystals prior to Mn-oxidation. IR peak intensity ratios reveal changes in biomolecular (carbohydrate, phosphate, and protein) composition during biologically catalyzed Mn-oxidation. In situ monitoring via ATR-FTIR of an active GB-1 biofilm and DRIFT data revealed an increase in extracellular protein (amide I and II) during Mn(II) oxidation, whereas transmission mode measurements suggest an overall increase in carbohydrate and phosphate moieties. The FTIR spectrum of biogenic Mn oxide comprises Mn-O stretching vibrations characteristic of various known Mn oxides (e.g., “acid” birnessite, romanechite, todorokite), but it is not identical to known synthetic solids, possibly because of solid-phase incorporation of biomolecular constituents. The results suggest that, when biogenic MnO _x accumulates on the surfaces of planktonic cells, adhesion of the bacteria to other negatively charged surfaces is hindered via blocking of surficial proteins.     

餐厨垃圾高温好氧生物减量菌种的筛选及特性

【背景】随着餐厨垃圾产生量的逐步提高,如何实现其快速降解,成为餐厨垃圾处理亟待解决的问题。餐厨垃圾的高温好氧生物减量技术是一种可以快速降解餐厨垃圾的有效方法。【目的】筛选能够适应餐厨垃圾环境且具有高效降解餐厨垃圾中有机物能力的菌株,以提高餐厨垃圾的降解效率和减量效果。【方法】采用温度梯度耐受性实验和餐厨垃圾浸出液高油高盐耐受性实验进行菌种初筛,并利用产酶培养基复筛及餐厨垃圾生物减量实验验证。【结果】通过初筛、复筛和功能验证,最终获得4株生物减量效果优良的菌株N3-1、C7、N3-3和G6-1,其对餐厨垃圾挥发性固体(volatile solid,VS)的降解率分别为36.95%、33.23%、32.83%和31.91%,是对照组的3.02、2.71、2.68和2.61倍。经鉴定,这4株菌分别属于热嗜油地芽孢杆菌(Geobacillus thermoleovorans)、史氏芽孢杆菌(Bacillus smithii)、热解木糖地芽孢杆菌(Geobacillus caldoxylosilyticus)和立陶宛地芽孢杆菌(Geobacillus lituanicus)。【结论】筛选出的4株菌均具有较强的餐厨垃圾原料适应性和高效的生物降解能力,为开发餐厨垃圾高温好氧复合菌剂奠定了基础,并为实现餐厨垃圾减量化、无害化处理和资源化利用提供了技术支持。     

转tcdA1B1杀虫基因的阴沟肠杆菌对4种农业害虫的杀虫活性与毒力

tcdA1B1为昆虫病原细菌一发光杆菌Photorhabdus luminescens的杀虫毒素基因。本文测定了转tcdA1B1基因的阴沟肠杆菌对甜菜夜蛾Spodoptera exigua、斜纹夜蛾Spodoptera litura、黄曲条跳甲Phyllotreta striolata和东亚飞蝗Locusta migratoria manilensis4种重要农业害虫的杀虫活性与毒力。在室内条件下,浓度为5．0×108cfu／mL的工程菌悬浮液,采用叶片浸渍法饲喂甜菜夜蛾2龄幼虫、斜纹夜蛾2龄幼虫、黄曲条跳甲成虫、东亚飞蝗2龄若虫,在11d、11d、15d、19d后的致死率分别为80．05％、81．83％、72．31％、39．74％;LT50分别为8．64d,8．38d、11．04d、28．22d。     

Dynamics of competitive population abundance of Lactobacillus plantarum ivi gene mutants in faecal samples after passage through the gastrointestinal tract of mice

AIM: This study aims to evaluate the impact of mutation of previously identified in vivo-induced (ivi) genes on the persistence and survival of Lactobacillus plantarum WCFS1 in the gastrointestinal (GI) tract of mice. METHODS AND RESULTS: Nine Lact. plantarum ivi gene replacement mutants were constructed, focussing on ivi genes that encode proteins with a predicted role in cell envelope functionality, stress response and regulation. The in vitro growth characteristics of the mutants appeared identical to those observed for the wild-type strain, which agrees with the recombination-based in vivo expression technology suggestion that these genes are not transcribed in the laboratory. Quantitative PCR experiments demonstrated differences in the relative population dynamics of the Lact. plantarum ivi mutants in faecal samples after passage through the GI tract of mice. CONCLUSIONS: The in situ competition experiments revealed a 100- to 1000-fold reduction of the relative abundance of three of the ivi gene mutants, harbouring deletions of genes predicted to encode a copper transporter, an orphan IIC cellobiose PTS and a cell wall anchored extracellular protein. SIGNIFICANCE AND IMPACT OF THE STUDY: These experiments clearly establish that the proteins encoded by these three genes play a key role in Lact. plantarum performance during passage of the GI tract.     

First exploration of Nitrobacter diversity in soils by a PCR cloning-sequencing approach targeting functional gene nxrA

Nitrite oxidoreductase (NXR) is the key enzyme responsible for the oxidation of NO(2)(-) to NO(3)(-) in nitrite-oxidizing bacteria. For the first time a molecular approach for targeting the nxrA gene was developed, encoding the catalytic subunit of the NXR, to study diversity of Nitrobacter-like organisms based on the phylogeny of nxrA gene sequences in soils. NxrA sequences of the Nitrobacter strains analysed (Nitrobacter hamburgensis, Nitrobacter vulgaris, Nitrobacter winogradskyi, Nitrobacter alkalicus) by PCR, cloning and sequencing revealed the occurrence of multiple copies of nxrA genes in these strains. The copy number and similarity varied among strains. The diversity of Nitrobacter-like nxrA sequences was explored in three soils (a French permanent pasture soil, a French fallow soil, and an African savannah soil) using a cloning and sequencing approach. Most nxrA sequences found in these soils (84%) differed from nxrA sequences obtained from Nitrobacter strains. Moreover, the phylogenetic distribution and richness of nxrA-like sequences was extremely variable depending on soil type. This nxrA tool extends the panel of functional genes available for studying bacteria involved in the nitrogen cycle.     

豆科植物根瘤内生细菌的发现及其研究进展

近年来研究报道显示,某些豆科植物与根瘤菌在形成固氮共生体的同时,其根瘤内还存在多种其他类群的内生细菌,该现象在根瘤菌研究领域越来越引起关注和重视。本文综述了根瘤内生土壤杆菌、非共生根瘤菌、其它细菌的发现、种类及其对共生关系和植物生长的影响等研究进展,同时对该研究方向提出一些初步观点和认识,旨在增加人们对根瘤微生态的了解,拓展根瘤菌研究与应用的视野。     

动物源细菌耐药性研究现状与对策

目前我国动物源细菌耐药现象十分普遍,多重耐药甚至泛耐药的菌株不断出现,给公共卫生和食品安全造成了重大威胁。文中从我国动物源耐药性研究的主要问题、细菌耐药性形成和传播机制以及耐药性防控策略等几个方面进行综述,以期为耐药性的研究和防控提供参考。