what is the function of bacteria present in the Caelum
of ruminants
Answers
Answer:
Rumen microbiology
Bacteria, protozoa, and fungi exist together in the cow’s rumen. Bacteria make up about half of the living organisms but do more than half of the rumen’s digestive work. Rumen bacteria are classified into fiber digesters, starch and sugar digesters, lactate using bacteria, and hydrogen-using bacteria. They cooperate together and cross feed.
Bacteria:
Bacteria make up about half of the living organisms inside of the rumen. However, they do more than half of the work in the rumen. The bacteria work together. Some breakdown certain carbohydrates and proteins which are then used by others. Some require certain growth factors, such as B-vitamins, which are made by others. Some bacteria help to clean up the rumen of others’ end products, such as hydrogen ions, which could otherwise accumulate and become toxic to other organisms. This is called “cross-feeding”.
Classification of Rumen Bacteria
Fiber–Digesting (or Cellulolytic) Bacteria:
The fiber-digesters are some of the “fussiest” bacteria in the rumen. They are very sensitive to acid. When a cow has acidosis (pH<6.0), the rumen produces a lower proportion of acetate to propionate because the fiber-digesters who primarily make acetate are not working well. Also, high levels of rumen available fat (generally over 5% of the diet) reduce the growth of the fiber-digesters. The exact reason for fat’s negative effect on the fiber-digesters is not known. Some think that it reduces the microbe’s ability to move nutrients into and out of its body. Others think that the fat coats fiber particles making it difficult for the fiber-digesting microbes to get in to do their work.
Bacterial species: Ruminococcus flavefacians, Ruminococcus albus, Bacteriodes succinogenes, Butyrivibrio fibrisolvens
Growth Requirements: Cellulose, Hemicellulose, Pectin
Many Also Require: Ammonia, Isoacids (Branched-Chain Amino Acids), Starch, B-vitamins - Fermentation Products: Acetate, Butyrate, Hydrogen (H2), Carbon Dioxide (CO2)
Rumen pH Requirement: High pH (above 6.0)
Fat Tolerance: Low
Susceptibility to Ionophores (Bovatec and Rumensin): Some are susceptible
Reproduction Speed: Slow
Starch and Sugar-Digesting (or Amylolytic) Bacteria:
Starch and sugar-digesters make up a significant part of the rumen’s bacterial population. Generally, high-producing dairy cows are fed diets containing more than 30% starches and sugars, so these bacteria are greatly needed. Even if a cow is on an all-straw diet, the fiber-digesters still never account for more than 25% of the rumen bacterial population. Starch and sugar-digesters are still present, cross-feeding
Sugar, Starch, Peptides, Amino Acids
Many Also Require: Ammonia, B-vitamins
Fermentation Products:
Propionate, Butyrate, Acetate, Lactate, Hydrogen (H2), Carbon Dioxide (CO2)
Rumen pH Requirement: Tolerate a lower (more acidic) pH (5.7)
Fat Tolerance:
Higher than fiber digesters
Susceptibility to Ionophors (Bovatec and Rumensin):
Most aren’t susceptible
Reproduction Speed:
Faster than fiber digesters
Streptococcus bovis, “The Rumen Weed”
Streptococcus bovisis present only when large amounts of starch or sugars are fed and pH is low. It produces lactic acid, a stronger acid than many of the other VFA’s produced in the rumen. When conditions are favorable for Streptococcus bovis, it will grow explosively
Lactate-Using Bacteria:
Includes: Megasphaera elsdenii, “The Rumen Maid”
As mentioned above, some bacteria, such as Streptococcus bovis, produce a strong acid called lactic acid. Megasphaera elsdenii uses lactic acid to grow. This helps to clean up the rumen a bit and raise rumen pH, aiding the growth of the acid-intolerant fiber-digesters.
Hydrogen-Using (or Methane) Bacteria:
Under normal rumen conditions, hydrogen (H2) does not accumulate in the rumen because it’s used by hydrogen-using bacteria, such as Methanobacterium ruminantium.
Growth Requirements: Carbon dioxide and hydrogen
Fermentation products: Methane
The methane bacteria commonly produce methane in this way:
4H2 + CO2 ---------> CH4 + 2H2O
Protozoa:
As much as 50% of the microbial mass in the rumen can be made up of protozoa. However, their role, as compared to the rumen bacteria, is not as significant. The protozoa are actually predators to the bacteria in the rumen --- they eat the bacteria for dinner! Protozoa are about 40 times the size of rumen bacteria.
The rumen protozoa produce fermentation end-products similar those made by the bacteria, particularly acetate, butyrate, and hydrogen. Rumen methane bacteria actually attach and live on the surface of rumen protozoa for immediate access to hydrogen.
Rumen protozoa eat large amounts of starch at one time and can store it in their bodies. This may help to slow down the production of acids that lower rumen pH, benefiting the rumen.
Answer:
Abstract
A cattle-yak, which is a hybrid between a yak (Bos grunniens) and cattle (Bos taurus), is an important livestock animal, but basic questions regarding its physiology and environmental adaptation remain unanswered. To address this issue, the present study examined the species composition and functional characteristics of rumen microorganisms in the cattle-yak of different ages (2 and 3 years old) by metagenomic analysis. We found that rumen microbial community composition was similar at the two ages. Firmicutes, Fibrobacteres, Euryarchaeota, Bacteroidetes, and Proteobacteria were the predominant phyla, with Firmicutes accounting for the highest percentage of bacteria in 2-year-old (48%) and 3-year-old (46%) animals. Bacterial species involved in lignocellulose degradation were detected in the rumen of adult cattle-yaks including Ruminococcus flavefaciens, Ruminococcus albus, Fibrobacter succinogenes, and Prevotella ruminicola, with F. succinogenes being the most abundant. A total of 145,489 genes were annotated according to the Carbohydrate-active Enzyme database, which identified glycoside hydrolases as the most highly represented enzyme family. Further functional annotation revealed specific microflora and genes in the adult rumen that are potentially related to plateau adaptability. These results could explain the heterosis of the cattle-yak and provide insight into mechanisms of physiologic adaptation in plateau animals.
1. Introduction
Ruminants have a diverse microbiota in their rumen including bacteria, fungi, archaea, protozoa, and viruses. These microorganisms can degrade the plant cell wall and fibrous substances that are converted into absorbable compounds such as proteins and volatile fatty acids (VFAs) [1, 2]. One study analyzing the rumen microbiome of Indian buffalo identified 2614 contigs encoding putative degradative enzymes [3], and another reported 42 operational taxonomic units representing the rumen bacterial community of adult buffalo [4]. Microbiome profile can vary according to the developmental stage; for instance, rumen microbial community composition in cows changes markedly from birth to the age of 2 years [5]. The rumen microbial environment of adult cattle is more stable and stricter than that of newborn calves, although it is unclear whether it also changes throughout adulthood.
A cattle-yak is the F1 hybrid between the female yak (Bos grunniens) and male cattle (Bos taurus), with the male cattle-yak being sterile. Cattle-yaks exhibit greater adaptability to harsh environments and provide more meat per weight than yak [6], along with milk, wool, fuel, and other products for communities living in the Qinghai-Tibet Plateau, making it an important livestock animal. Cattle-yaks live at high altitudes and feed mostly by grazing; they can also grow normally during the dry grass period of the Plateau when the food supply is limited. The rumen of cattle-yaks is presumed to contain microorganisms with lignocellulose-degrading capability that enable adaptation to the plateau environment [7], but few studies have investigated rumen microbiota community composition and function in these animals.
To address this issue, we carried out a metagenomic analysis of the rumen microbiome of cattle-yak at two different ages (2 and 3 years of age). Our results reveal the diversity of the rumen microbial community in ruminants and suggest potential mechanisms of adaptation to the unique plateau environment.
2. Materials and Methods
2.1. Ethics Statement
Experiments involving animals were carried out in accordance with regulations for the Administration of Affairs Concerning Experimental Animals (Ministry of Science and Technology, China; revised in June 2004). Sample collection was carried out according to the guidelines of the Ethics Committee for the Care and Use of Laboratory Animals of Gansu Agricultural University.
2.2. Animals and Sample Collection
Six male 2- and 3-year-old healthy cattle-yaks (yak ♀×Jersey cattle ♂, each) were obtained from a farm in Gannan Tibetan Autonomous Prefecture (Gansu Province, China). Rumen samples (50 ml, containing fluid and feed particles) were collected from each animal after slaughter and immediately frozen in liquid nitrogen and stored at −80°C until use.
2.3. DNA Extraction and High-Throughput Sequencing
Genomic DNA was extracted from rumen fluid and purified using the TIANamp Stool DNA Kit (Tiangen Biotech, Beijing, China) according to the manufacturer’s instructions and sent to Gansu Meita Biomedical Co. (Lanzhou, China) for high-throughput sequencing.
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