Min Chen

Bio: Min Chen is an academic researcher from New York State Department of Health. The author has contributed to research in topics: Microcystis & Muramic acid. The author has an hindex of 2, co-authored 3 publications receiving 351 citations.

Effect of Monensin and Lasalocid-Sodium on the Growth of Methanogenic and Rumen Saccharolytic Bacteria

Abstract: It is thought that monensin increases the efficiency of feed utilization by cattle by altering the rumen fermentation. We studied the effect of monensin and the related ionophore antibiotic lasalocid-sodium (Hoffman-LaRoche) on the growth of methanogenic and rumen saccharolytic bacteria in a complex medium containing rumen fluid. Ruminococcus albus, Ruminococcus flavefaciens, and Butyrivibrio fibrisolvens were inhibited by 2.5 μg of monensin or lasalocid per ml. Growth of Bacteroides succinogenes and Bacteroides ruminicola was delayed by 2.5 μg of monensin or lasalocid per ml. Populations of B. succinogenes and B. ruminicola that were resistant to 20 μg of either drug per ml were rapidly selected by growth in the presence of each drug at 5.0 μg/ml. Selenomonas ruminantium was insensitive to 40 μg of monensin or lasalocid per ml. Either antibiotic (10 μg/ml) inhibited Methanobacterium MOH, Methanobacterium formicicum, and Methanosarcina barkeri MS. Methanobacterium ruminantium PS was insensitive to 40 μg of monensin or 20 μg of lasalocid per ml. The methanogenic strain 442 was insensitive to 40 μg of monensin but sensitive to 10 μg of lasalocid per ml. The results suggest that monensin or lasalocid acts in the rumen by selecting for succinate-forming Bacteroides and for S. ruminantium, a propionate producer that decarboxylates succinate to propionate. The selection could lead to an increase in rumen propionate formation. Selection against H2 and formate producers, e.g. R. albus, R. flavefaciens, and B. fibrisolvens, could lead to a depression of methane production in the rumen.

Difference in sporogenous bacterial populations in thermophilic (55 degrees C) and mesophilic (35 degrees C) anaerobic sewage digestion.

Abstract: Spores, sporeforming vegetative cells, and asporogenous populations were enumerated in two semicontinuous anaerobic fermentors digesting municipal primary sludge at 35 and 55 degrees C for more than 87 days In the 35 degrees C fermentor, the anaerobic total population was 3125 X 10(6)/ml, with 250 X 10(6)/ml being sporogenous The populations that digest casein, starch, pectin, and cellulose were 231 X 10(6), 592 X 10(6), 262 X 10(6), and 73 X 10(6)/ml, respectively, with 28 X 10(6), 67 X 10(6), 34 X 10(6), and 15 X 10(6)/ml being sporogenous, respectively The sporeformers accounted for 80 to 200% of each of the respective populations In the 55 degrees C fermentor, the anaerobic total population was 5125 X 10(6)/ml, with 3366 X 10(6)/ml being sporogenous The populations that digest casein, starch, pectin, and cellulose were 977 X 10(6), 1907 X 10(6), 758 X 10(6), and 112 X 10(6)/ml, respectively, with 478 X 10(6), 1106 X 10(6), 433 X 10(6), and 51 X 10(6)/ml, respectively, being sporogenous The sporeformers represented 455 to 657% of each of the respective populations The numbers of thermophilic sporeforming vegetative cells in the 55 degrees C fermentor were 90 to 198 times higher than their counterparts in the 35 degrees C fermentor Most sporeformers were in the vegetative state in the 35 and 55 degrees C fermentors After 18 days of fermentation at 55 degrees C, sporeformers carried out most of the digestion; however, the digestion was shared by both sporeformers and asporogenous bacteria after 87 days of fermentation In the 35 degrees C fermentor, asporogenous bacteria digested most of the sludge During the 18- and 87-day experimental periods, sporeformers were never predominant

Mycolicibacterium lacusdiani sp. nov., an Attached Bacterium of Microcystis aeruginosa

Abstract: In eutrophic water, attached bacteria of Microcystis play an important role in the formation, development, and degradation of Microcystis blooms. A novel actinobacterium, designated as JXJ CY 35T, was isolated from the culture mass of Microcystis aeruginosa FACHB-905 (Maf) collected from Lake Dianchi, Yunnan Province, China. Strain JXJ CY 35T was gram-positive, acid-fast staining, aerobic, with short rod-shaped cells, positive for catalase, and negative for oxidase. The isolate was able to grow at 10.0–36.0°C, pH 4.0–10.0, and tolerate up to 5.0% (w/v) NaCl, with optimal growth at 28°C, pH 7.0–8.0, and 0% (w/v) NaCl. Cell-wall peptidoglycan contains aspartic acid, glutamic acid, glycine, and alanine, with mannose, ribose, galactose, and arabinose as whole-cell sugars. Polar lipids consist of diphosphatidylglycerol (DPG), phosphatidylethanolamine (PE), glycolipid (GL1-3), phosphoglycolipid (PGL), phosphatidylinositol (PI), and unidentified lipid (L1). The predominant menaquinone was MK-9. Major fatty acids (>10%) were C17:1ω7c (37.0%) and C18:1ω9c (18.9%). The complete genome sequence of strain JXJ CY 35T was 6,138,096 bp in size with a DNA G + C content of 68.3%. Based on 16S rRNA gene sequences, it has 98.2% similarity to Mycolicibacterium arabiense JCM 18538T. The digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values between strain JXJ CY 35T and the closest five type strains M. arabiense JCM 18538T, M. goodii ATCC 700504T, M. mageritense DSM 44476T, M. austroafricanum DSM 44191T, and Mycobacterium neglectum CECT 8778T were 52.1, 20.3, 20.3, 20.6, and 19.8%, and 92.7, 75.5, 75.6, 76.0, and 75.2%, respectively. On the basis of the above taxonomic data and differences in physiological characteristics from the closely related type strain, strain JXJ CY 35T was determined to represent a novel species of genus Mycolicibacterium, for which the name Mycolicibacterium lacusdiani sp. nov., is proposed. The type strain is JXJ CY 35T (=KCTC 49379T = CGMCC 1.17501T). Different inoculation dosages of the type strain JXJ CY 35T could exhibit different effects on the growth of Maf and its toxin synthesis and release. Strain JXJ CY 35T could promote the growth of Maf by providing it with available phosphorus, nitrogen, probably vitamins, and plant growth hormones.

Simple medium that preserves low concentrations of Escherichia coli for use in the water bacteriology proficiency test.

Abstract: A medium containing (per liter) 6.8 g of sodium acetate trihydrate, 3.4 g of potassium dihydrogen phosphate, and 0.1 g of magnesium sulfate heptahydrate (medium pH, 5.85 plus/minus 0.05) was developed for use in a water bacteriology proficiency test. The medium maintained 80 to 100 % viability of inoculated Escherichia coli at temperatures up to 31 degrees C for at least 12 days, while the concentrations of bacteria in the medium were as low as 20 bacteria per 100 ml. The medium remained stable after a year of storage. It has been used successfully to preserve bacteria in nine statewide bacteriology proficiency tests for potable and nonpotable water and has also been used in a nationwide pilot test. This report presents the results of these tests.

Energy contributions of volatile fatty acids from the gastrointestinal tract in various species

Abstract: The VFA, also known as short-chain fatty acids, are produced in the gastrointestinal tract by microbial fermentation of carbohydrates and endogenous substrates, such as mucus. This can be of great advantage to the animal, since no digestive enzymes exist for breaking down cellulose or other complex carbohydrates. The VFA are produced in the largest amounts in herbivorous animal species and especially in the forestomach of ruminants. The VFA, however, also are produced in the lower digestive tract of humans and all animal species, and intestinal fermentation resembles that occurring in the rumen. The principal VFA in either the rumen or large intestine are acetate, propionate, and butyrate and are produced in a ratio varying from approximately 75:15:10 to 40:40:20. Absorption of VFA at their site of production is rapid, and large quantities are metabolized by the ruminal or large intestinal epithelium before reaching the portal blood. Most of the butyrate is converted to ketone bodies or CO2 by the epithelial cells, and nearly all of the remainder is removed by the liver. Propionate is similarly removed by the liver but is largely converted to glucose. Although species differences exist, acetate is used principally by peripheral tissues, especially fat and muscle. Considerable energy is obtained from VFA in herbivorous species, and far more research has been conducted on ruminants than on other species. Significant VFA, however, are now known to be produced in omnivorous species, such as pigs and humans. Current estimates are that VFA contribute approximately 70% to the caloric requirements of ruminants, such as sheep and cattle, approximately 10% for humans, and approximately 20-30% for several other omnivorous or herbivorous animals. The amount of fiber in the diet undoubtedly affects the amount of VFA produced, and thus the contribution of VFA to the energy needs of the body could become considerably greater as the dietary fiber increases. Pigs and some species of monkey most closely resemble humans, and current research should be directed toward examining the fermentation processes and VFA metabolism in those species. In addition to the energetic or nutritional contributions of VFA to the body, the VFA may indirectly influence cholesterol synthesis and even help regulate insulin or glucagon secretion. In addition, VFA production and absorption have a very significant effect on epithelial cell growth, blood flow, and the normal secretory and absorptive functions of the large intestine, cecum, and rumen. The absorption of VFA and sodium, for example, seem to be interdependent, and release of bicarbonate usually occurs during VFA absorption.(ABSTRACT TRUNCATED AT 400 WORDS)

A net carbohydrate and protein system for evaluating cattle diets: I. Ruminal fermentation.

Abstract: The Cornell Net Carbohydrate and Protein System (CNCPS) has a kinetic submodel that predicts ruminal fermentation. The ruminal microbial population is divided into bacteria that ferment structural carbohydrate (SC) and those that ferment nonstructural carbohydrate (NSC). Protozoa are accommodated by a decrease in the theoretical maximum growth yield (.50 vs .40 g of cells per gram of carbohydrate fermented), and the yields are adjusted for maintenance requirements (.05 vs .150 g of cell dry weight per gram of carbohydrate fermented per hour for SC and NSC bacteria, respectively). Bacterial yield is decreased when forage NDF is < 20% (2.5% for every 1% decrease in NDF). The SC bacteria utilize only ammonia as a N source, but the NSC bacteria can utilize either ammonia or peptides. The yield of NSC bacteria is enhanced by as much as 18.7% when proteins or peptides are available. The NSC bacteria produce less ammonia when the carbohydrate fermentation (growth) rate is rapid, but 34% of the ammonia production is insensitive to the rate of carbohydrate fermentation. Ammonia production rates are moderated by the rate of peptide and amino acid uptake (.07 g of peptide per gram of cells per hour), and peptides and amino acids can pass out of the rumen if the rate of proteolysis is faster than the rate of peptide utilization. The protein-sparing effect of ionophores is accommodated by decreasing the rate of peptide uptake by 34%. Validation with published data of microbial flow from the rumen gave a regression with a slope of .94 and an r2 of .88.

Methane production by ruminants: its contribution to global warming

Abstract: The aim of this paper is to review the role of methane in the global warming scenario and to examine the contribution to atmospheric methane made by enteric fermentation, mainly by ruminants. Agricultural emissions of methane in the EU-15 have recently been estimated at 10.2 million tonnes per year and represent the greatest source. Of these, approximately two-thirds come from enteric fermentation and one-third from livestock manure. Fermentation of feeds in the rumen is the largest source of methane from enteric fermentation and this paper considers in detail the reasons for, and the consequences of, the fact that the molar percentage of the different volatile fatty acids produced during fermentation influences the production of methane in the rumen. Acetate and butyrate promote methane production while propionate formation can be considered as a competitive pathway for hydrogen use in the rumen. The many alternative approaches to reducing methane are considered, both in terms of reduction per animal and reduction per unit of animal product. It was concluded that the most promising areas for future research for reducing methanogenesis are the development of new products/delivery systems for anti-methanogenic compounds or alternative electron acceptors in the rumen and reduction in protozoal numbers in the rumen. It is also stressed that the reason ruminants are so important to mankind is that much of the world's biomass is rich in fibre. They can convert this into high quality protein sources (i.e. meat and milk) for human consumption and this will need to be balanced against the concomitant production of methane.

The rumen bacteria

Abstract: This chapter will deal mainly with the characteristics of bacteria from the rumen that have been successfully cultivated in the laboratory. For some ecosystems, particularly those dominated by slow-growing or specialized microorganisms, it has become clear that only a very small fraction (often <1%) of the total microbial diversity has been recovered by cultural methods (Amann et al., 1995) and that descriptions of the ecosystem based on the available isolated strains can be highly misleading. These discrepancies are apparent both from comparison of direct microscopic and culturable counts, and from direct analyses of ribosomal RNA sequence diversity. In the rumen, organisms surviving in significant numbers must have growth rates sufficient to counteract the constant dilution due to turnover of rumen contents, and there are indications that the discrepancies may be less extreme. Leedle et al (1982) found that the culturable count fluctuated with time after feeding between 14% and 74% of the direct microscopic count in the rumens of animals fed on two different diets. Since the viability of several rumen species is known to change upon starvation, the lower figure could partly reflect changes in the viability of known, culturable species. Thus it is to be hoped that the major obstacles to cultivation of the most numerous rumen bacteria have been overcome by the development of sufficiently rigorous anaerobic methods and of suitable isolation media. It remains likely, however, that some functionally important groups (e.g. obligate syntrophs) may not have been recovered; Mclnerney et al (1981) used co-culture with Desulfovibrio in the presence of sulphate to isolate a fatty acid-oxidizing bacterium similar to Syntrophomonas wolfei from bovine rumen contents.

Methane mitigation in ruminants: from microbe to the farm scale

Abstract: Decreasing enteric methane (CH4) emissions from ruminants without altering animal production is desirable both as a strategy to reduce global greenhouse gas (GHG) emissions and as a means of improving feed conversion efficiency. The aim of this paper is to provide an update on a selection of proved and potential strategies to mitigate enteric CH4 production by ruminants. Various biotechnologies are currently being explored with mixed results. Approaches to control methanogens through vaccination or the use of bacteriocins highlight the difficulty to modulate the rumen microbial ecosystem durably. The use of probiotics, i.e. acetogens and live yeasts, remains a potentially interesting approach, but results have been either unsatisfactory, not conclusive, or have yet to be confirmed in vivo. Elimination of the rumen protozoa to mitigate methanogenesis is promising, but this option should be carefully evaluated in terms of livestock performances. In addition, on-farm defaunation techniques are not available up to now. Several feed additives such as ionophores, organic acids and plant extracts have also been assayed. The potential use of plant extracts to reduce CH4 is receiving a renewed interest as they are seen as a natural alternative to chemical additives and are well perceived by consumers. The response to tannin- and saponin-containing plant extracts is highly variable and more research is needed to assess the effectiveness and eventual presence of undesirable residues in animal products. Nutritional strategies to mitigate CH4 emissions from ruminants are, without doubt, the most developed and ready to be applied in the field. Approaches presented in this paper involve interventions on the nature and amount of energy-based concentrates and forages, which constitute the main component of diets as well as the use of lipid supplements. The possible selection of animals based on low CH4 production and more likely on their high efficiency of digestive processes is also addressed. Whatever the approach proposed, however, before practical solutions are applied in the field, the sustainability of CH4 suppressing strategies is an important issue that has to be considered. The evaluation of different strategies, in terms of total GHG emissions for a given production system, is discussed.