Amnibacterium soli sp. nov., an actinobacterium isolated from grass soil

Soil microbiome analysis reveals effects of periodic waterlogging stress on sugarcane growth

Sugarcane is one of the major agricultural crops with high economic importance in Thailand. Periodic waterlogging has a long-term negative effect on sugarcane development, soil properties, and microbial diversity, impacting overall sugarcane production. Yet, the microbial structure in periodically waterlogged sugarcane fields across soil compartments and growth stages in Thailand has not been documented. This study investigated soil and rhizosphere microbial communities in a periodic waterlogged field in comparison with a normal field in a sugarcane plantation in Ratchaburi, Thailand, using 16S rRNA and ITS amplicon sequencing. Alpha diversity analysis revealed comparable values in periodic waterlogged and normal fields across all growth stages, while beta diversity analysis highlighted distinct microbial community profiles in both fields throughout the growth stages. In the periodic waterlogged field, the relative abundance of Chloroflexi, Actinobacteria, and Basidiomycota increased, while Acidobacteria and Ascomycota decreased. Beneficial microbes such as Arthrobacter, Azoarcus, Bacillus, Paenibacillus, Pseudomonas, and Streptomyces thrived in the normal field, potentially serving as biomarkers for favorable soil conditions. Conversely, phytopathogens and growth-inhibiting bacteria were prevalent in the periodic waterlogged field, indicating unfavorable conditions. The co-occurrence network in rhizosphere of the normal field had the highest complexity, implying increased sharing of resources among microorganisms and enhanced soil biological fertility. Altogether, this study demonstrated that the periodic waterlogged field had a long-term negative effect on the soil microbial community which is a key determining factor of sugarcane growth.

Lacisediminihabitans profunda gen. nov., sp. nov., a member of the family Microbacteriaceae isolated from freshwater sediment

A novel Gram-stain-positive bacterial strain, CHu50b-6-2^T, was isolated from a 67-cm-long sediment core collected from the Daechung Reservoir at a water depth of 17 m, Daejeon, Republic of Korea. The cells of strain CHu50b-6-2^T were aerobic non-motile and formed yellow colonies on R2A agar. The phylogenetic analysis based on 16S rRNA gene sequencing indicated that the strain formed a separate lineage within the family Microbacteriaceae, exhibiting 98.0%, 97.7% and 97.6% 16S rRNA gene sequence similarities to Glaciihabitans tibetensis KCTC 29148^T, Frigoribacterium faeni KACC 20509^T and Lysinibacter cavernae DSM 27960^T, respectively. The phylogenetic trees revealed that strain CHu50b-6-2^T did not show a clear affiliation to any genus within the family Microbacteriaceae. The chemotaxonomic results showed B1α type peptidoglacan containg 2, 4-diaminobutyric acid (DAB) as the diagnostic diamino acid, MK-10 as the predominant respiratory menaquinone, diphosphatidylglycerol, phosphatidylglycerol, and an unidentified glycolipid as the major polar lipids, anteiso-C_15:0, iso-C_16:0, and anteiso-C_17:0 as the major fatty acids, and a DNA G + C content of 67.3 mol%. The combined genotypic and phenotypic data showed that strain CHu50b-6-2^T could be distinguished from all genera within the family Microbacteriaceae and represents a novel genus, Lacisediminihabitans gen. nov., with the name Lacisediminihabitans profunda sp. nov., in the family Microbacteriaceae. The type strain is CHu50b-6-2^T (= KCTC 49081^T = JCM 32673^T).

Amnibacterium setariae sp. nov., an endophytic actinobacterium isolated from dried foxtail

A Gram-stain positive, short rod-shaped, aerobic, motile by means of gliding, yellow-pigmented actinobacterium, designated strain DD4a^T, was isolated from dry yellow foxtail. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain DD4a^T is closely related to Amnibacterium soli MB78^T (98.4% similarity), Amnibacterium kyonggiense KSL51201-037^T (98.2%) and Amnibacterium endophyticum 1T4Z-3^T (97.43%). Strain DD4a^T forms yellow colonies on R2A agar medium. The peptidoglycan was found to contains diaminopimelic acid (which is a diagnostic cell wall diamino acid), alanine, glutamic acid and lysine. The polar lipids diphosphatidylglycerol, phosphatidylglycerol, six unidentified glycolipids and an unidentified polar lipid were found to be present in strain DD4a^T. The major cellular fatty acids anteiso-C_15:0 (42.9%) and iso-C_16:0 (34.6%) were found in strain DD4a^T. The predominant respiratory quinones were found to be MK-11 and MK-12. The DNA G+C content of strain DD4a^T is 73.9 mol%. DNA-DNA relatedness of strain DD4a^T with A. soli MB78^T, A. kyonggiense KSL51201-037^T, and A. endophyticum 1T4Z-3^T were 53.3% (± 1.1%), 47.0% (± 0.5%), and 47.9% (± 0.9%), respectively. The digital DNA-DNA hybridisation and average nucleotide identity values between strain DD4a^T and A. kyonggiense KSL51201-037^T were determined to be 26.1% and 82.7%. On the basis of phenotypic, genotypic, chemotaxonomic and phylogenetic analysis, DD4a^T represents a novel member of the genus Amnibacterium, for which the name Amnibacterium setariae sp. nov., is proposed. The type strain of Amnibacterium setariae is DD4a^T (= KACC 19817^T = JCM 32878^T).

Amnibacterium flavum sp. nov., a novel endophytic actinobacterium isolated from bark of Nerium indicum Mill

A Gram-stain-positive, aerobic, short-rod-shaped, non-spore-forming actinobacterial strain, designated M8JJ-5^T, was isolated from a surface-sterilized bark of Neriumindicum Mill. collected from Guizhou, China, and investigated by a polyphasic approach to determine its taxonomic position. Strain M8JJ-5^T grew optimally without NaCl at 28 °C and at pH 7.0-8.0. Substrate mycelia and aerial mycelia were not formed, and no diffusible pigments were observed on the media tested. Phylogenetic analysis based on the 16S rRNA gene sequence showed that strain M8JJ-5^T was most closely related to the type strains of genus Amnibacterium, and shared highest 16S rRNA gene sequence similarity of 97.29 % to Amnibacterium kyonggiense KSL51201-037^T. The DNA G+C content of strain M8JJ-5^T was 68.6 mol%. The cell-wall peptidoglycan contained l-2,4-diaminobutyric acid and MK-12, MK-11 were the major menaquinones. The predominant polar lipids were diphosphatidylglycerol, phosphatidylglycerol, an unidentified glycolipid, an unidentified phospholipid and an unidentified lipid, while the major fatty acids were iso-C16 : 0, anteiso-C15 : 0 and anteiso-C17 : 0. On the basis of phylogenetic, chemotaxonomic and phenotypic data, strain M8JJ-5^T can be characterized to represent a novel species of the genus Amnibacterium, for which the name Amnibacteriumflavum sp. nov. is proposed. The type strain is M8JJ-5^T (=KCTC 49089^T=CGMCC 1.16390^T).

Diversity, Novelty, and Antimicrobial Activity of Endophytic Actinobacteria From Mangrove Plants in Beilun Estuary National Nature Reserve of Guangxi, China

Endophytic actinobacteria are one of the important pharmaceutical resources and well known for producing different types of bioactive substances. Nevertheless, detection of the novelty, diversity, and bioactivity on endophytic actinobacteria isolated from mangrove plants are scarce. In this study, five different mangrove plants, Avicennia marina, Aegiceras corniculatum, Kandelia obovota, Bruguiera gymnorrhiza, and Thespesia populnea, were collected from Beilun Estuary National Nature Reserve in Guangxi Zhuang Autonomous Region, China. A total of 101 endophytic actinobacteria strains were recovered by culture-based approaches. They distributed in 7 orders, 15 families, and 28 genera including Streptomyces, Curtobacterium, Mycobacterium, Micrococcus, Brevibacterium, Kocuria, Nocardioides, Kineococcus, Kytococcus, Marmoricola, Microbacterium, Micromonospora, Actinoplanes, Agrococcus, Amnibacterium, Brachybacterium, Citricoccus, Dermacoccus, Glutamicibacter, Gordonia, Isoptericola, Janibacter, Leucobacter, Nocardia, Nocardiopsis, Pseudokineococcus, Sanguibacter, and Verrucosispora. Among them, seven strains were potentially new species of genera Nocardioides, Streptomyces, Amnibacterium, Marmoricola, and Mycobacterium. Above all, strain 8BXZ-J1 has already been characterized as a new species of the genus Marmoricola. A total of 63 out of 101 strains were chosen to screen antibacterial activities by paper-disk diffusion method and inhibitors of ribosome and DNA biosynthesis by means of a double fluorescent protein reporter. A total of 31 strains exhibited positive results in at least one antibacterial assay. Notably, strain 8BXZ-J1 and three other potential novel species, 7BMP-1, 5BQP-J3, and 1BXZ-J1, all showed antibacterial bioactivity. In addition, 21 strains showed inhibitory activities against at least one "ESKAPE" resistant pathogens. We also found that Streptomyces strains 2BBP-J2 and 1BBP-1 produce bioactive compound with inhibitory activity on protein biosynthesis as result of translation stalling. Meanwhile, Streptomyces strain 3BQP-1 produces bioactive compound inducing SOS-response due to DNA damage. In conclusion, this study proved mangrove plants harbored a high diversity of cultivable endophytic actinobacteria, which can be a promising source for discovery of novel species and bioactive compounds.

Amnibacterium endophyticum sp. nov., an endophytic actinobacterium isolated from Aegiceras corniculatum

A Gram-stain-positive, aerobic, non-motile, non-spore-forming and short-rod-shaped actinobacterium, designated strain 1T4Z-3^T, was isolated from a piece of surface-sterilized branch of Aegiceras corniculatum collected from the Cotai Ecological Zones in Macao, China. Comparative 16S rRNA gene sequence analysis showed that strain 1T4Z-3^T was clearly affiliated to the genus Amnibacterium and exhibited 97.9 % gene sequence similarity to Amnibacterium kyonggiense JCM 16463^T, 97.3 % gene sequence similarity to Amnibacterium soli JCM 19015^T and less than 96.4 % gene sequence similarities to other genera of the family Microbacteriaceae. Strain 1T4Z-3^T had L-2,4-diaminobutyric acid as the diagnostic cell-wall diamino acid. The major fatty acids (>10 % of total fatty acids) were iso-C16 : 0 (46.6 %) and anteiso-C15 : 0 (27.3 %). The predominant menaquinones of strain 1T4Z-3^T were MK-11 (81.4 %) and MK-12 (14.1 %). The polar lipids comprised diphosphatidylglycerol, phosphatidylglycerol, six unidentified glycolipids, four unidentified phospholipids and two unidentified lipids. The DNA G+C content of strain 1T4Z-3^T was 71.4 mol%. Based on the phylogenetic, phenotypic and chemotaxonomic features, strain 1T4Z-3^T is considered to represent a novel species of the genus Amnibacterium, for which the name Amnibacterium endophyticum sp. nov. is proposed. The type strain of Amnibacterium endophyticum is 1T4Z-3^T (=KCTC 39983^T=CGMCC 1.16066^T).

The nasopharyngeal microbiota of beef cattle before and after transport to a feedlot

Background

The nasopharyngeal (NP) microbiota plays an important role in bovine health, comprising a rich and diverse microbial community. The nasopharynx is also the niche for potentially pathogenic agents which are associated with bovine respiratory disease (BRD), a serious and costly illness in feedlot cattle. We used 14 beef heifers from a closed and disease-free herd to assess the dynamics of the NP microbiota of cattle that are transported to a feedlot. Cattle were sampled prior to transport to the feedlot (day 0) and at days 2, 7, and 14.

Results

The structure of the NP microbiota changed significantly over the course of the study, with the largest shift occurring between day 0 (prior to transport) and day 2 (P < 0.001). Phylogenetic diversity and richness increased following feedlot placement (day 2; P < 0.05). The genera Pasteurella, Bacillus, and Proteus were enriched at day 0, Streptococcus and Acinetobacter at day 2, Bifidobacterium at day 7, and Mycoplasma at day 14. The functional potential of the NP microbiota was assessed using PICRUSt, revealing that replication and repair, as well as translation pathways, were more relatively abundant in day 14 samples. These differences were driven mostly by Mycoplasma. Although eight cattle were culture-positive for the BRD-associated bacterium Pasteurella multocida at one or more sampling times, none were culture-positive for Mannheimia haemolytica or Histophilus somni.

Conclusions

This study investigated the effect that feedlot placement has on the NP microbiota of beef cattle over a 14-d period. Within two days of transport to the feedlot, the NP microbiota changed significantly, increasing in both phylogenetic diversity and richness. These results demonstrate that there is an abrupt shift in the NP microbiota of cattle after transportation to a feedlot. This may have importance for understanding why cattle are most susceptible to BRD after feedlot placement.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-017-0978-6) contains supplementary material, which is available to authorized users.

Aurantimicrobium minutum gen. nov., sp. nov., a novel ultramicrobacterium of the family Microbacteriaceae, isolated from river water

A Gram-stain-positive, aerobic, non-motile, curved (selenoid), rod-shaped actinobacterium, designated KNCT, was isolated from the 0.2 μm-filtrate of river water in western Japan. Cells of strain KNCT were ultramicrosized (0.04-0.05 μm3). The strain grew at 15-37 °C, with no observable growth at 10 °C or 40 °C. The pH range for growth was 7-9, with weaker growth at pH 10. Growth was impeded by the presence of NaCl at concentrations greater than 1 %. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain KNCT showed relatively high sequence similarity (97.2 %) to Alpinimonas psychrophila Cr8-25T in the family Microbacteriaceae. However, strain KNCT formed an independent cluster with cultured, but as-yet-unidentified, species and environmental clones on the phylogenetic tree. The major cellular fatty acids were anteiso-C15 : 0 (41.0 %), iso-C16 : 0 (21.8 %), C16 : 0 (18.0 %) and anteiso-C17 : 0 (12.9 %), and the major menaquinones were MK-11 (71.3 %) and MK-12 (13.6 %). The major polar lipids were phosphatidylglycerol and two unknown glycolipids. The cell-wall muramic acid acyl type was acetyl. The peptidoglycan was B-type, and contained 3-hydroxyglutamic acid, glutamic acid, aspartic acid, glycine, alanine and lysine, with the latter being the diagnostic diamino acid. The G+C content of the genome was unusually low for actinobacteria (52.1 mol%), compared with other genera in the family Microbacteriaceae. Based on the phenotypic characteristics and phylogenetic evidence, strain KNCT represents a novel species of a new genus within the family Microbacteriaceae, for which the name Aurantimicrobium minutum gen. nov., sp. nov. is proposed. The type strain of the type species is KNCT ( = NBRC 105389T = NCIMB 14875T).